[dropcap]While[/dropcap] cleaning for Pesach, the most fundamental aspect of knowledge we need is a clear definition of what we are looking for. Although it is true that for many, Pesach cleaning is just an excuse to do a thorough “spring cleaning”, we will see that the Torah has very specific definitions of what we are supposed to be looking for and what we should be focusing on cleaning.
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<h2>Defining Terms</h2>
There are a few verses that are important to be familiar with in order to have a greater level of clarity in this issue:
<blockquote>For seven days you shall eat matzos, but on the first day <span style="text-decoration: underline;">you shall put to rest</span> (<em>tashbisu)</em> <span style="text-decoration: underline;">sourdough</span> (<em>se’or</em>) from your homes, <span style="text-decoration: underline;">because anyone who eats leaven</span> (<em>chametz)</em> will be punished with <em>kares</em>…[ref]Exodus 12:15[/ref]</blockquote>
<blockquote>For seven days <span style="text-decoration: underline;">no sourdough</span> (<em>se’or</em>) shall be <span style="text-decoration: underline;">found</span> in your homes, <span style="text-decoration: underline;">because anyone who eats a leavening agent</span> is liable to the punishment of <em>kares</em>…[ref]Exodus 12:19[/ref]</blockquote>
<blockquote>For seven days matzos shall be eaten, and <span style="text-decoration: underline;">there shall not be seen any leavened grain</span> (<em>chametz</em>) and <span style="text-decoration: underline;">there shall not be seen any leavening agents</span> (<em>se’or</em>) in all of your boundaries.[ref]Exodus 13:7[/ref]</blockquote>
<h3><em>Chametz</em> – Leavened Items of the Five Grains</h3>
The Talmud[ref]Beitzah 7b[/ref] defines the two terms we find in the verses above. <em>chametz</em> has two unique features:
<ol>
    <li>It is edible</li>
    <li>It is not fermented enough that it can facilitate fermentation in other products</li>
</ol>
The Torah says that someone who eats <em>chametz</em> on Pesach is liable for <em>kares</em>. This penalty only applies to eating a <em>kezayis</em> (about 30 grams) within 4 minutes. However, the Torah still prohibits eating less than that amount even though there is no official penalty. We will see below that this prohibition of eating even the tiniest amount applies to all edible <em>chametz</em>, even if it is in a mixture.
<h3><em>Se’or</em> – Sourdough Starter Derived From the Five Grains</h3>
The same piece of Talmud says that <em>se’or</em> (sourdough starter) has two unique features:
<ol>
    <li>It is not edible</li>
    <li>It is so fermented itself that it can actually be a leavening agent for other products</li>
</ol>
The same amounts we mentioned above by eating <em>chametz</em> apply to <em>se’or</em> as well.
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<h2><em>Bitul</em> – the Nullification of Chametz</h2>
<h3>What is <em>Bitul</em> (Nullification)?</h3>
We saw above in Exodus 12:15 that the verse enjoins us with the word ‘<em>tashbisu</em>’ - “put to rest” all <em>chametz</em>. The Talmud[ref]Pesachim 6b[/ref] implies that this verse means to declare in one’s heart that his <em>chametz</em> is ownerless and like the dust of the earth.
<h3><strong>When do we Need to do this Nullification?</strong></h3>
We saw above that the verse wrote “<em>but</em> on the first day you shall nullify”. In <em>chumash</em>, the word “but” (“<em>ach</em>” in Hebrew) usually comes to exclude something, but it's difficult to understand that exclusion in the context of our verse. We know from verse 12:19 that you clearly may not have any <em>chametz</em> around for the entire seven days of Pesach. Therefore, the word “but” in 12:15 couldn’t have meant what we would have thought, that part of the first day of Pesach is excluded from the prohibition of having <em>chametz</em> around.

The Talmud[ref]Pesachim 4b[/ref] explains as follows: the word “but” perforce means that there is a significant day, previous to the first official day of Pesach which, inasmuch as it is just previous to the first day can be seen similar in a certain sense to the first day” of Pesach, which is previous to the rest of the days of Pesach. The word “but” is coming to exclude part of that first day, <em>Erev Pesach </em>on the 14<sup>th</sup> of Nissan in the Jewish Calendar, from the general permission to have <em>chametz</em> around during the year. The verse is therefore understood as follows “<em>…</em>but<em> already on </em>Erev Pesach<em> you shall nullify all </em>chametz<em> from your homes…</em>”

This teaches us the first and possibly the most fundamental of all of the laws of Pesach. We have a Torah obligation to nullify our <em>chametz</em>. The same piece of Talmud addresses this issue further, saying that the verse also indicates a certain time on <em>Erev Pesach</em> by which you need to have made this declaration, that being by the time of the arrival of the 6<sup>th</sup> halachic hour of the day.

The Mishnah[ref]Pesachim 11b, 21a[/ref] follows the opinion of Rebbe Yehudah that the sages enacted this <em>g'zeirah</em> out of concern that on a cloudy day people may become confused about the time and come to miss the <em>zman bitul</em>. Therefore they instituted that we must make the <em>bitul</em> declaration by the end of the 4<sup>th</sup> halachic hour on the morning of <em>Erev Pesach</em>.
<h3>What Type of <em>Chametz</em> Must be Nullified? (<em>Chametz and Se'or</em>)</h3>
Rashi to Exodus 12:19 quotes a Mechiltah[ref]Ch. 12, Parshah 10, Sif 69[/ref] (a very early source of <em>midrash halacha</em> - talmudic legal exegesis) which teaches that the reason why the Torah needed to mention the prohibition of eating <em>chametz</em> (in 12:15) and <em>se’or</em> (in 12:19) is because we could not have derived the one prohibition even if we had known the other. This is because of how we defined the two materials in Beitzah above: <em>chametz</em> is edible and can’t ferment other products, whereas <em>se’or</em> is inedible and is able to ferment other products. Therefore, if I had only known the prohibition of eating <em>se’or</em> I would have thought that it is prohibited specifically because it has the ability to facilitate the leavening process; and since <em>chametz</em> does not facilitate leavening, it might not need to be forbidden. Alternatively, if I had only known the prohibition of eating <em>chametz</em> I would have thought that it is prohibited specifically because it is edible; but <em>se'or,</em> which is inedible, not. Therefore, the Torah needed to write both verses. once we have both, we know that it is prohibited to eat both <em>chametz</em> and <em>se’or</em> on Pesach.

This brings us to our next major building block. In Exodus 12:15 and 12:19, the Torah actually tells us the reason that we need to nullify <em>se’or</em> already from <em>Erev Pesach</em>: because<em> </em>eating <em>se'or</em> on Pesach is so severe that it leads to the penalty of <em>kares</em>. From this point, we now work backwards to understand the <em>din. </em>Even though the verse which mentions nullifying (Exodus 12:15) only mentions <em>se’or</em> explicitly, nevertheless the obligation to nullify applies equally to both <em>chametz</em> and <em>se’or</em>, since one who eats either on Pesach is liable for <em>kares</em>.

Therefore, we need to nullify by the end of the 4<sup>th</sup> halachic hour on <em>Erev Pesach</em> minimally all <em>chametz </em>and all <em>se'or</em> in our possession that could produce a <em>chiyuv kares </em>if eaten.
<h3>A Mixture with a Full <em>Kezayis</em> of <em>Chametz</em> in it</h3>
The Gemara[ref]Pesachim 43a[/ref] brings a <em>braysah </em>discussing two opinions of how to expound the verse:
<blockquote>Any form of leavening agent you shall not eat on Pesach, in all of your encampments you shall eat matzos[ref]Exodus 12:20[/ref]”</blockquote>
Rebbe Eliezer holds that this verse comes to teach that there is a prohibition from the Torah to eat <em>chametz bta'aroves</em> (a mixture of <em>chametz</em> and non-<em>chametz</em>) and also <em>chametz numksheh</em> (<em>chametz</em> that was once edible but became hardened and unfit for human consumption)<em>. </em>The <em>Chachamim</em> say that the verse is only coming to forbid eating <em>chametz nuksheh, </em>but that <em>chametz</em> <em>bta'aroves </em>is not forbidden by the Torah to eat.

<em></em>The halachah is that it is not prohibited by the Torah with punishment of <em>kares</em> to eat a mixture with <em>chametz</em>, as long as the mixture contains within it less than a <em>kezayis</em> (about 30 grams). When the mixture does contain a <em>kezayis</em> of <em>chametz</em>, the Rishonim differ as to how to understand the halacha:
<ul>
    <li>The Rambam[ref]Hilchos <em>chametz</em> Umatzah 1:6[/ref] and the Rif[ref]Beginning of Perek Elu Ovrin[/ref] say that it is prohibited by the Torah to eat but one who does is not liable for <em>kares</em>.</li>
    <li>The Ramban[ref]Sefer Milchamas Hashem, beginning of Perek Elu Ovrin[/ref] and most other Rishonim understand that one who eats this type of mixture is liable the penalty of <em>kares</em>.</li>
</ul>
The halachah follows the opinion of the Ramban. Therefore, it follows that there would even be an obligation from the Torah to nullify such a mixture[ref]Mishnah Brurah 442:1[/ref].
<h3>Small Crumbs that are Less than a <em>Kezayis</em></h3>
<strong></strong>Based on all of the above, is there an obligation to nullify small crumbs of <em>chametz</em>? The Gemara[ref]Pesachim 6b[/ref] deals with this question by stating the following unexpected rule: small crumbs of <em>chametz</em> that are less than a <em>kezayis</em> are in-and-of-themselves insignificant and thus do not require nullification. This follows from the rule that any <em>chametz </em>which couldn't produce a <em>chiuv kares</em> does not require nullification. We will discuss more about crumbs of <em>chametz</em> in the next section.
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<h2><em>Bal Yeira’eh U’val Yeimatzeh</em> – The Prohibition of Keeping <em>Chametz</em> in My Possession</h2>
We saw above that the Torah[ref]Exodus 12:15[/ref] requires us to nullify any <em>chametz</em> we have by the 6<sup>th</sup> hour on <em>Erev Pesach</em>. This nullification of <em>chametz</em> is a mental act of dissolving all importance from and all connection to our <em>chametz</em>. In a manner of speaking one could say that by nullifying our <em>chametz,</em> we are removing it from our world completely, even though that process is only taking place on a mental level.

In addition we saw two other verses, Exodus 12:19 and 13:7, which instruct us in the prohibition of leaving <em>chametz</em> around during Pesach. We will now look deeper into this prohibition.
<h3>Which <em>Chametz</em> Does the Torah Prohibit Keeping Around?</h3>
Before proceeding, we need to ask a fundamental question: if the Torah demands that we nullify all of our <em>chametz</em> on <em>Erev Pesach,</em> and that nullification is a valid form of “getting rid of" our <em>chametz,</em> then what is the verse talking about when it says there is a prohibition to “keep <em>chametz</em> around during Pesach?" What <em>chametz</em> would be left around?

There are two possible ways to understand the Torah’s intention here. The first way fits together with everything we have learned until now: the only time that you transgress the prohibition of <em><em>bal yeira’eh</em> and <em>bal yeimatzeh</em></em> is when you didn’t perform the nullification on your <em>chametz,</em> either because you forgot or you somehow acquired <em>chametz</em> on <em>Erev Pesach </em>after you had already nullified the rest. The second involves redefining the type of <em>chametz</em> which these particular prohibitions address.
<h4>Case 1: Someone who Forgot to Do the Nullification or Acquired New <em>Chametz</em> on Pesach</h4>
What is a person supposed to do in a situation where he didn’t properly nullify his <em>chametz</em>? At this point he is in a predicament, since after the sixth hour of <em>Erev Pesach</em> sets in, it becomes forbidden to derive any benefit from <em>chametz</em>. Interestingly enough, inasmuch as that is true, the “nullification in one’s heart” can’t work. When you do the nullification before the sixth hour, you do it to a substance that is permissible to you and that you have ownership of, so your statement of nullification has "teeth". After the sixth hour and through the rest of Pesach however, remaining or additional <em>chametz</em> sits in your possession, but it is in a state where you can’t make a declaration about it.

Our sages teach in [ref]Pesachim 6a[/ref and also in [ref]Pesachim6b[/ref] that in such a situation, one's only recourse is to burn the <em>chametz</em> completely. This “puts it to rest” in the actual physical sense, as opposed to on a merely legal level. This is certainly included in the understanding of what the Torah wants from us by saying make sure that <em>chametz </em>and <em>se'or </em>are neither seen or found in your possession on Pesach. See more in [ref]Shulchan Aruch 446:1[/ref]
<h4>Case 2: A Mixture of <em>Chametz</em></h4>
There is a second way to answer to the dilemma we raised above.  We saw a clear indication in the Torah that the reason you have to nullify your <em>chametz</em> is so that you don’t come to transgress the prohibition of eating it and be liable or the penalty of <em>kares.</em> The question we now face is whether the same logic applies to the prohibitions of <em>bal yeira’eh </em>and<em> bal yeimatzeh</em>.

One more verse in the Torah teaches us an important extension to the laws of <em>chametz</em>.
<blockquote>Any form of leavening agent you shall not eat on Pesach, in all of your encampments you shall eat matzos[ref]Exodus 12:20[/ref]”</blockquote>
The Talmud[ref]Tractate Pesachim 43a[/ref] brings a two-way <em>Tannaic </em>discussion as to what this verse means.
<ul>
    <li>Rebbe Eliezer explains that the words “<em>any</em> form” (of leavening agent), come to add and include the case of <em>chametz bta'aroves </em>in the prohibition of eating <em>chametz </em>even though there is no punishment of <em>kares.</em></li>
</ul>
<h3><em>Chametz Nuksheh</em></h3>
The Gemara [ref]Pesachim 43a[/ref], while discussing Rebbe Eliezer's approach, points out that once we know that the above verse includes the prohibition to eat a <em>ta'aroves</em> <em>chametz, </em>all the more so we can extend that obligation to<em> chametz nuksheh</em>. According to Rebbe Eliezer this is more severe than a <em>ta'aroves</em> of edible <em>chametz </em>since <em>nuksheh</em> was once full-fledged <em>chametz</em>.

The <em>Chachamim</em> take a more lenient approach in explaining the above verse, saying that <em>ta'aroves</em> containing edible<em> chametz </em>is not at all forbidden to eat as far as the Torah is concerned. The phrase “<em>any</em> form" of leavening agent in the verse is only talking about <em>chametz nuksheh.</em>
<h3><em>Se'or</em> vs. <em>Chametz Nuksheh</em></h3>
What exactly is this “<em>chametz nuksheh</em>” that we are talking about, here? Isn't that the <em>se'or</em> that we were learning about <em>earlier</em>? Aren't they both examples of inedible <em>chametz</em>?

The answer is no. There is a fundamental distinction between <em>se’or</em> and <em>chametz nuksheh</em>. Namely, <em>se’or</em> has the quality of facilitating the fermentation of other items, causing them to become <em>chametz</em>. It is true that <em>se’or</em> is inedible yet it is still forbidden and is punishable by kares because it can cause other items to firment and become chametz, however, here by <em>chametz nuksheh </em>we are talking about something that is both inedible and unable to cause fermentation in other substances. Technically, the only thing that makes "<em>chametz nuksheh" </em>prohibited at all is that it was derived from <em>chametz</em> or was itself once <em>chametz</em>. This is why we refer to this stuff as <em>chametz nuksheh</em> or <em>hardened</em> <em>chametz</em>.

The halacha regarding <em>bal yira'eh and bal yimatzeh </em>follows the opinion of Rebbe Eliezer[ref]Be'er Hagolah 442:1[/ref]. Therefore, a person must not keep around in his possession during Pesach any mixture which contains chametz. What is interesting is that since the halacha follows Rebbe Eliezer regarding <em>bal yira'eh </em>and <em>bal yimatzeh </em>it should follow that a person should not be allowed to keep <em>chametz nuksheh</em> in his possession during Pesach either. The Magen Avraham[ref]Orach Chaim 447:46[/ref] proves from the Shulchan Aruch that this is not the case. In fact there is no prohibition to keep <em>chametz nuksheh </em>around as far as teh law of <em>bal yira'eh and bal yimatzeh.</em>

What is the rationale for this distinction? We see the answer in the Shulchan Aruch[ref] Orach Chaim 442:1[/ref]. He teaches us that there is a distinction between a mixture of <em>chametz</em> that is edible and a mixture of <em>chametz</em> that is inedible. The prohibition to keep <em>chametz</em> in a mixture around during Pesach only applies to a mixture of fully-edible <em>chametz</em>.
<h3>Small Crumbs with Less than a <em>Kezayis</em> of<em> Chametz</em></h3>
The Chazon Ish[ref]Orach Chaim 116:13 “V’Hagra”[/ref] explains that even though the Gemara in Pesachim 6b (see above) says that small crumbs of <em>chametz</em> are automatically nullified, nevertheless with regards to <em>Bal Yeira’eh</em> and <em>Bal Yeimatzeh,</em> you must get rid of the small crumbs, since part of the rationale for the Torah’s law is to prevent you from even coming to transgress the <em>issur</em> of eating <em>chametz</em> even in a case where you couldn’t get <em>kares.</em>

It follows from here that part of the obligation to clean our homes requires looking for and getting rid of small crumbs of <em>chametz</em> as well even though they are already nullified according to the law of nullification of <em>chametz</em>. This obligation is stated clearly in the Chayeh Adam[ref]Klal 119:10[/ref] and in the Shulchan Aruch Harav[ref]442:28[/ref] as well as in the Mishnah Brurah[ref]442:33[/ref]. However, as we will see ahead once the crumbs are less than a <em>kezayis</em> and they are rendered inedible for people due to their becoming attached to floors, walls, etc. at that point we don’t even have an obligation to get rid of them. Such crumbs that are found in places like tables, chairs, counters, cupboards and the like still retain their status as food and would thus need to be destroyed[ref]See Mishneh Brurah 442:33 as well as look ahead for more clarification[/ref].
<h3>Absorptions of Taste in Eating and Cooking Vessels</h3>
The law of absorptions is “<em>ta’am k’ikar</em>” —the taste absorptions of a food are like the actual food as regards the halacha. We therefore face a problem of <em>Bal Yeira’eh</em> and <em>Bal Yeimatzeh </em>with all of our year-round pots, pans, and other eating and cooking vessels. These vessels still have <em>chametz</em> taste absorptions in them, therefore even if we just to leave these vessels around the house during the <em>chag</em>, we should have to kasher them all before Pesach to get rid of all of those absorptions.

There is another rule, mentioned in Gemara and Rishonim that we should be aware of. The Gemara[ref]Pesachim 30a[/ref] says that vessels which we aren’t planning to on Pesach can be cleaned and put away before the festival, without transgressing the laws of <em>Bal Yeira’eh</em> and <em>Bal Yeimatzeh</em>. The Ravan explains that the <em>issur</em> of <em>Bal Yeira’eh</em> and <em>Bal Yeimatzeh</em> don’t apply to chametz that is absorbed inside something else. It is still <em>chametz</em> but it is not “seen” or “found” when it is in its absorbed state. As a result we now see that regarding both the law of nullification and the law of Bal Yira’eh and Bal Yimatzeh chametz absorbed inside vessles poses no problem and no need to do anything special for Pesach. We need to clean them and put them away only as a precautionary measure lest we come to use them on Pesach unwittingly.
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<h2>Kashering Vessels for Pesach</h2>
All of the above is true only regarding <em>chametz</em> vessels which we don’t plan to use during the <em>chag</em>. For vessels which you do wish to use, absorptions of <em>chametz</em> in it which can bring a person to the transgression of the <em>issur chametz</em> that requires a special process of “kashering” the vessel in order to eradicate the absorptions in order that we may use the vessel on Pesach. We will not discuss all of the laws of kashering vessels right now but in general the rule for kashering is that “k’bolo kach polto” meaning the method of how the pot is normally used i.e. cooking with water, roasting, etc is the method in which it needs to be koshered. See our article on kashering vessels for more details.
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<h2>“<em>Bedikah</em> and <em>Biyur</em> <em>Chametz</em>” Search and Destroy all <em>Chametz</em></h2>
The first Mishnah in Tractate Pesachim teaches us about a special rabbinic obligation on the night of the 14<sup>th</sup> of Nissan. We must go through any place under our ownership that may have <em>chametz</em> in it and check by candlelight. This is called <em>bedikah,</em> or checking. In the ensuing discussions in the Gemara, it becomes clear that whatever <em>chametz</em> we find during this search should be taken and burned on the following morning. The problem is that this practice don’t seem to be derived from any of the Torah injunctions we read above.
<ul>
    <li>We learned from that on <em>Erev Pesach</em> a person has to nullify all of his <em>chametz.</em> (Exodus 12:15)</li>
    <li>We spent quite a while defining what fits into that prohibition.</li>
    <li>We also saw that if a person didn’t do that nullification he is transgressing the prohibition of <em>bal yeira’eh</em> and <em>bal yeimatzeh</em>. (Exodus 12:19 and 13:7)</li>
    <li>In addition we learned that <em>bal yira'eh </em>and<em> bal yimatzeh </em>require me to get rid of any fully edible <em>chametz</em> even if it is in a mixture.</li>
</ul>
But none of these sources describe the need to go around the house and "check" for c<em>hametz</em>.
<h3>The Reason for this Rabbinic Injunction</h3>
What then is the idea behind this "seek and destroy mission" we find discussed in the Gemara? Rabbeinu Nissim in his [ref]gloss to Tractate Pesachim 1a in Dapei Harif "elah"[/ref] asks this famous question, and he and he gives the following answer. It is clear that the Torah requires you to get rid of your <em>chametz</em> before the 6<sup>th</sup> hour of <em>Erev Pesach</em>. There are two ways to do that.
<ol>
    <li>One way is to search through your house and find anything that fits the description of <em>chametz</em> and destroy it.</li>
    <li>The other way is to nullify your <em>chametz</em> by the 6<sup>th</sup> hour.</li>
</ol>
As far as the Torah is concerned, either of these methods will suffice to prevent you from transgressing the prohibitions of <em>bal yeira’eh</em> and <em>bal yeimatzeh</em>. However, the Rabbis felt that given the nature of people and the severity of eating <em>chametz</em> on Pesach (the penalty of <em>kares)</em> it was necessary to make a <em>g'zeirah</em> or fence. The concern was that since the nullification process is founded on the sincerity of a person’s declaration, then depending on who he is and what he has in his possession, his declaration (and thus his nullification) might not be valid.

Alternatively, they were worried that since <em>chametz</em> is permitted throughout the year and people are so used to putting it in their mouths without thinking, that just such an occurrence might happen on Pesach with a nice piece of <em>chametz</em> that he will be excited about, thus undermining the nullification. Therefore, the Rabbis instituted these additional laws on top of the Torah that force us to search and destroy all <em>chametz</em> before Pesach.
<h3>This Obligation Applies to <em>all</em> Forms of C<em>hametz</em></h3>
Based on what we have learned, one would think that this rabbinic law would apply to the same type of <em>chametz</em> as the nullification we learned about before. However, when we look deeper into this topic we find an interesting idea. Remember that we are only obligated to nullify <em>chametz</em> that could bring to the penalty of <em>kares</em>. On the other hand the prohibitions of <em>bal yeira’eh</em> and <em>bal yeimatzeh</em> apply to any <em>chametz</em> that is edible. The question is: when the Rabbis enacted this <em>g'zeirah</em>, did they pattern it after the obligation to nullify or after the prohibition to keep <em>chametz</em> lying around?

The Tur[ref]Siman 442[/ref]understands that the Rabbis patterned the laws of <em>bedikah</em> and <em>biyur</em> on the foundations of <em>bal yeira’eh</em> and <em>bal yeimatzeh</em>. Therefore, a person would have an obligation to physically search though his house and destroy all <em>chametz</em>, <em>se’or</em>, and <em>ta'aroves</em>. However, inedible <em>chametz</em> would still be permissible to leave around on Pesach according to him. Rabbeinu Tam[ref]Pesachim 42a "V'elu"[/ref]as well as the Shulchan Aruch[ref]Orach Chaim 447:12[/ref] hold that while Tur's logic is well founded, the Rabbis nevertheless took an additional step here in order to streamline the law and thus avoid confusion. Thus according to them, one has an obligation to search for and destroy all <em>chametz,</em> even <em>chametz nuksheh </em>since it is still somewhat edible
<h3>The Difference Between a Mixture of Inedible <em>Chametz</em> and <em>Chametz Nuksheh</em></h3>
In the final accounting of the halacha there is a distinction between an inedible mixture of <em>chametz </em>which one need not bother getting rid of or even checking for and between <em>chametz nuksheh</em> which a person must actually go around the house and check for [ref]Mishneh Brurah 442:2[/ref]. The Mishneh Brurah explains this distinction by saying that the definition of <em>chametz nuksheh </em>is that although a person wouldn't eat it in general it is still seen as food and under duress a person might eat it. The type of mixture we were talking about above that one is exempt from worrying about altogether is one that one would eat under any circumstances - see below.

In essence than the obligation to do "<em>bedikas chametz" </em>checking the house and destroying all chametz comes to add on and streamline the law of <em>bal yira'eh </em>and <em>bal yimatzeh </em> so that we must now get rid of any chametz that is even somewhat edible regardless of whether it is <em>b'ein </em>(whole and separate) or <em>bta'aroves.</em>
<h3>The Two Types of Items not Included in the Law of <em>Bedikas Chametz</em></h3>
Based on the above, there are specific types of items that are not technically called <em>chametz</em> and are therefore not included in the rabbinic obligation to search out and destroy all <em>chametz</em>.
<ol>
    <li>The first, as mentioned above, is <em>chametz</em> that has become so inedible that not even a dog would eat it (<em>nifsal l'achilas kelev</em>)[ref]Pesachim 15b, Beraisa. See "Afra b'Alma"[/ref].</li>
    <li>The second is <em>chametz</em> that, because of its situation is seen as having a status of non-food, regardless of its technical edibility[ref]Mishnah in Pesachim 45a "<em>Batzek Shbesidkei Areiva</em>..."[/ref].</li>
</ol>
<h3>Small Crumbs of <em>Chametz</em> Around the House</h3>
The second category gives us a very practical idea of how to deal with small crumbs of <em>chametz. </em>We saw above that one must get rid of small, somewhat edible crumbs, so as not to transgress <em>bal yira'eh </em>and <em>bal yimatzeh</em>. We now qualify that statement, adding that once the tiny crumbs have become attached to a surface that we wouldn't eat off of, they lose food status altogether.

The picture of how to relate to those small crumbs of <em>chametz</em> in our cleaning is now clear. Any small crumbs that are in places or on surfaces where we might still be tempted to eat them must be cleaned and gotten rid of before Pesach; however, crumbs that are on the floor, or are laying on or stuck to any surface that we would not eat off of are rendered <em>tafel</em> to that surface and take on the status of non-food.

Furthermore, even if small crumbs are on a surface that we would eat off of, we can fulfill our obligation to get rid of them by spraying some sort of heavy cleaning agent on them, causing them to become fully inedible, and thus fulfilling our obligation to destroy them.
<h3>How and When do we Fulfill this Mitzvah?</h3>
The Talmud[ref]Pesachim 6a[/ref] teaches that the basic obligation to search for and destroy <em>chametz</em> starts from 30 days before Pesach. It is from that point that we should start to develop the consciousness of getting prepared for the festival. The mitzvah breaks up into two parts:
<ol>
    <li>The first is the “mental and legal” part.</li>
    <li>The second is the “ceremonial part”.</li>
</ol>
The more well known part of the obligation is the ceremonial part, referring to the night of the 14<sup>th</sup> of Nissan when we make a blessing with a candle and a feather and go around the house checking all of the cracks and crevices to make sure there is no <em>chametz</em> of any kind left in our possession. This physical searching out and destroying of the <em>chametz</em> is our main fulfilment of the injunction.

In cases where for whatever reason a person will not be able to fulfill all that is incumbent upon him during the ceremonial search, the mental and legal obligation (which anyways applies to everyone equally) takes up the slack. One example is a person who is travelling before Pesach and won’t be home in time to search. Another example is someone who has such a large amount of cleaning to do that he has to start cleaning in advance. Both of these scenarios can frequently apply to our modern lives. It's assumed though that most of us today are able fulfill the bulk of our obligation to search out and destroy our <em>chametz</em> during the 30 days leading up to the festival.

The Rabbis distinguished between two different times of day with regards to the search for <em>chametz:</em> the daylight hours and the nighttime. <em>Bedikah </em>done during the daylight hours is valid for cleaning parts of the house or items that can be viewed in their full detail in plain sunlight. Areas and items in the home whose detail can only be seen well under candle or incandescent light must be checked at nighttime. This principle, along with what we have learned above, helps us focus on cleaning each place in the home and each item in the correct way and at the correct time.

The night of the 14<sup>th</sup> of Nissan is used to clean any remaining areas we haven’t reached. But even if a person has already cleaned everything in the home, there is a custom to lay 10 pieces of bread around the house so that the ceremonial search will still be meaningful.
<h3>Which Places did the Rabbis Require me to Search and Where can we Simply rely on Nullification?</h3>
One of the fundamental principles of Pesach cleaning, taught in Talmud[ref]Mishnah in Pesachim 2a "<em>Makom Shemachnisim bo Chametz…</em>"[/ref], is that a person is only obligated to search for <em>chametz</em> in a place where he is likely to find it. Thus, one must clean all areas in the home that one normally takes <em>chametz</em> into. It also applies to any area where it is reasonable to assume that <em>chametz</em> might be found. For those who have toddlers or small children, the scope of this mitzvah is obviously much greater, since the nature of small children is to distribute <em>chametz</em> randomly into any and all spaces of a house. We collect any <em>chametz</em> we find in these places and either dispose of well before <em>Erev Pesach</em> or save it to be burned that morning.
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<h2>Declarations and Burning <em>Chametz</em></h2>
We say two different declarations during the process of searching for and destroying <em>chametz.</em> The first declaration is made just after the completion of the ceremonial part of the mitzvah on the night of the 14<sup>th</sup>. In this declaration, we render nullified any <em>chametz</em> that we may not have found and destroyed. The reason we say so is because we have by now officially completed the searching process, so any <em>chametz</em> that is still in our possession that we may not have found and destroyed for whatever reason must be nullified.

Since it is not yet forbidden to eat <em>chametz</em>, and we still plan to keep a small amount of <em>chametz</em> on the side to be eaten up before the end of the 4<sup>th</sup> hour of the following morning. We also have <em>chametz</em> set aside to burn the following morning, as the Rabbis instructed. We want our declaration to be meaningful in light of all that, so after burning our last remaining <em>chametz,</em> we make a much broader declaration rendering null and void any <em>chametz</em> of any kind.
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<h2>In Summary</h2>
We have reviewed the major principles of cleaning for Pesach:
<ol>
    <li>The Torah forbids us from consuming either <strong><em>chametz</em></strong> or <strong><em>se’or</em></strong>, in any amount from the <strong>6<sup>th</sup> hour of <em>Erev Pesach</em></strong> until after Pesach is over. This is true whether the <em>chametz</em> is by itself (<strong><em>b'ein</em></strong>) or it is in a mixture (<strong><em>ta'aroves</em></strong>). It doesn’t matter how much <em>chametz</em> is in the mixture, all <em>ta'arovos</em> are prohibited.</li>
    <li>The Torah obligates us to put our <em>chametz</em> "to rest" before the 6<sup>th</sup> halachic hour on <em>Erev Pesach,</em> either by <strong>destroying</strong> it or through mental <strong>nullification</strong>. The Rabbis enacted as a fence that we must make this declaration by the end of the 4<sup>th</sup> halachic hour.</li>
    <li>This Torah-prescribed formula for nullification applies to “<em>chametz</em>” (i.e. edible leavened grain products) and “<em>se’or</em>” (inedible leavening agent that is derived from the five grains), as they are the two forms of <em>chametz</em> that can cause a person to be liable for the <strong>penalty of <em>kares</em>.</strong></li>
    <li>The Torah obligates us to <strong>nullify</strong> a mixture (<strong><em>ta'aroves</em></strong>) that has more than a <strong><em>kezayis</em></strong> (30 grams) of edible <em>chametz</em> in it.</li>
    <li>The reason the Torah demands this “nullification process” of us is in order to prevent us from coming to eat either <em>chametz</em> or <em>se’or</em> on Pesach and thereby incurring the penalty of <em>kares</em>.</li>
    <li>In addition, the Torah obligates us to <strong>not have in our possession any type of <em>chametz</em></strong> that is fully edible during Pesach<em>.</em> Practically, this adds a <em>ta'aroves</em> of <em>chametz</em>, regardless of how little <em>chametz</em> there is in the mixture. This also requires us to get rid of small edible crumbs of <em>chametz</em>. It is for this reason that many products require special <em>kashrus</em> supervision for Pesach and also why we must facilitate a sale of many items in our kitchen as well as certain other products.</li>
    <li><strong>Pots, pans, and other utensils</strong> that we don't plan to use for Pesach can be <strong>cleaned off and put away</strong> since any absorbed <em>chametz</em> doesn't pose a problem of <em>bal yeira'eh </em>and <em>bal yeimatzeh. </em>If we want to use a certain vessel for Peach it needs to be <strong>kashered</strong> so that the absorptions of <em>chametz</em> in it are eradicated and don't come out into the food we consume from that vessel on Pesach.</li>
    <li>The Rabbis made a fence around the above laws by instituting the obligation to <strong>search out and destroy</strong> by fire any form of even slightly edible <em>chametz. </em>Practically this comes to include the obligation to search and get rid of<em> chametz nuksheh.</em> It is for this reason that certain art supplies and other various household items might need to be put away and sold for Pesach.</li>
    <li>The <em>chiyuv bedikah</em> requires getting rid of all even somewhat edible <em>chametz</em>, but any <em>chametz</em> that is rendered <strong>totally inedible</strong> even for a dog is not included, nor is any <em>chametz</em> that has become <strong><em>tafel </em>to a surface that we wouldn't eat off of</strong>. This will help to explain why certain cosmetics and products are okay to keep around and in our possession during Pesach even though they may have contained some additive of <em>chametz </em>in them.</li>
    <li>In cases where a person has an overwhelming amount of cleaning to do, they <strong>may start their cleaning from 30 days before</strong> the festival.</li>
    <li>In such a case, the person should clean those places and items whose <strong>every detail is visible in plain sunlight</strong> during the day. Places and items whose detail is only visible by candle or incandescent light must be cleaned at night.</li>
    <li>The only <em>chametz</em>-like object we may leave around the house during Pesach is <em>chametz</em> that has been rendered so inedible that not even a dog would eat it or <em>chametz</em> that has for other reasons lost the status of food altogether.</li>
</ol>
May Hashem recognize our efforts to clarify and understand our obligation to clean for Pesach and grant us the strength to succeed and excel in performing this great mitzvah. May we merit to clean our homes of all <em>chametz</em> and truly come to experience the freedom of a life uncontrolled by our <em>yetzer hara</em>.
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