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Sahih Muslim: Book 003, Number 0684:

    Abu Musa reported: There cropped up a difference of opinion between a group of Muhajirs (Emigrants) and a group of Ansar (Helpers) (and the point of dispute was) that the Ansar said: The bath (because of sexual intercourse) becomes obligatory only when the semen spurts out or ejaculates. But the Muhajirs said: When a man has sexual intercourse (with the woman), a bath becomes obligatory (no matter whether or not there is seminal emission or ejaculation). Abu Musa said: Well, I satisfy you on this (issue). He (Abu Musa, the narrator) said: I got up (and went) to 'A'isha and sought her permission and it was granted, and I said to her: O Mother, or Mother of the Faithful, I want to ask you about a matter on which I feel shy. She said: Don't feel shy of asking me about a thing which you can ask your mother, who gave you birth, for I am too your mother. Upon this I said: What makes a bath obligatory for a person? She replied: You have come across one well informed! The Messenger of Allah (may peace be upon him) said: When anyone sits amidst four parts (of the woman) and the circumcised parts touch each other a bath becomes obligatory. (Source)


Commentary of Imam Al-Nawawi on the Hadith

    The saying of the prophet – peace be upon him- ‘If one sits between a woman’s fours (shu’biha Al-arba) and then fatigues her’

    In another narration the word ‘Ashu’biha’ is used. The scholars have disagreed about the intended meaning of ‘shu’biha Al-arba’ (the fours) for some said that it means the arms and the legs, while others have said that it refers to the legs and thighs, and other said it means the legs and the edge of the pubic area. Al-Qadi Ayad chose the meaning of the four areas surrounding the vagina. The word (Shu’b) means areas, its singular form being (Shu’bah). As for those who say (Ashba’iha) that is the plural of the word (Shu’b).

    The word Aj-hada-ha (fatigue her) means to plow her, which was also stated by Al-Khatabi. Others have said it means to make her reach exhaustion as in the phrase ‘she made him toil and labor till he was exhausted’. Al-Qadi Ayad – may Allah rest his soul- said ‘Primarily, the word (Jahada’ha) means that the man exerted his effort working in a woman, where the word (Juh’d) means energy and refers to motion by describing the type of work. This is similar to his (the prophet) saying ‘he who plowed her’ meaning he who penetrated her by his motion. Otherwise, what other fatigue could a man experience because of her, and Allah knows best.

    The meaning of the hadith is that the necessity to wash is not limited to when semen is ejaculated, rater it is when the penile head (Hash-fa, lit. "the head of the male member," i.e. head of the penis) penetrates the vagina, then it is necessary for the man and the woman to wash. There is no disagreement on this today, even though there was disagreement on this by some of the early companions and others later. However, an agreement was later reached and this is what we have shown and presented previously.

    Our companions have said that if the penile head has penetrated A WOMAN’S ANUS, or A MAN’S ANUS, or AN ANIMAL’S VAGINA or ITS ANUS then it is necessary to wash whether the one being penetrated is alive OR DEAD, YOUNG OR OLD, whether it was done intentionally or absentmindedly, whether it was done willfully or forcefully. This also applies if the woman places the male member inside her while the man is asleep, whether the penis is erect or not, whether the penis is circumcised or uncircumcised. All these situations require that the person committing the act and the one the act is committed on must wash themselves, unless the person committing the act or the person the act is committed on is a young male or female. In that case it cannot be said that the person must wash, for they do not have the responsibility, rather it is said that this person is in a state of impurity. If that person can discern (the sexual act) then his guardian can command him to wash just as he commands him to perform the ablution washing for prayers. For if he prays without washing, his prayer has not been performed correctly; likewise if he doesn’t wash after he reaches puberty he must be forced to wash. If he washed as a youth and then reaches puberty, then he does not have to repeat the washing.

    Our companions have said that intercourse occurs when a healthy male’s penile head completely penetrates (an orifice), as has been unanimously agreed. Thus, when the penile head has completely disappeared (inside the orifice), then all the regulations concerning washing apply. It is unanimously agreed that it is not necessary that the entire penile shaft penetrate to apply the regulations of washing. If part of the penile head penetrates, then the regulations of washing are not imposed as is agreed, except by an odd few of our companions who said that even in this case all the regulations of washing apply. However, this opinion is wrong, rejected and abandoned.

    If the male member was severed and what remained was less than the length of the penile head, then none of the washing regulations apply. If the part remaining was equal in length to the penile head length then that part must completely penetrate for the regulation of washing to apply. If the part remaining was greater in length to the penile head length then there are two famous opinions for our companions. The most correct is that if the portion that penetrates is equal to the length of the penile head, then the regulations for washing apply. The other opinion is that none of the regulations for washing apply until the entire remaining length of the penile shaft completely penetrates and Allah knows best.

    If a man wraps a sheath around his male member and then ejaculates inside a woman’s vagina, then there are three opinions from our companions. The most famous is that the man must wash. The second is that he does not have to wash because he ejaculated inside the sheath. The third is that if the sheath is thick and prevents climax and wetness (in the vagina) then washing is not necessary, otherwise it is necessary and Allah knows best.

    If a woman inserts (in her vagina) AN ANIMAL’S PENIS she must wash, and if she inserts A DETACHED PENIS (thakaran maktu-an, lit. "a severed male member"; a marital aid perhaps!?) there are two opinions; the most correct is that she must wash.