Loki

"You are scared," said Odin.
The great beast sniffed the air. "I scent treachery and trickery," said the wolf, his amber eyes flashing in the moonlight. "And although I think your Gelipnir may only be a ribbon, I will not consent to be tied up by it."
"You? You who broke the strongest, biggest chains there ever were? You are scared by this band?" said Thor.
"I am scared of nothing," growled the wolf. "I think it is rather that you creatures are scared of me."
Odin scratched his bearded chin. "You are not stupid, Fenrir. There is no treachery here. But I understand your reluctance. It would take a brave warrior to consent to be tied up with bonds he could not break. I assure you, as the father of the gods, that if you cannot break a band like this—a veritable silken ribbon, as you say—then we gods will have no reason to be afraid of you, and we will set you free and let you go your own way."
A long growl, from the wolf. "You like, All-father. You like in the way that some folk breathe. If you were to tie me up in bonds I could not escape from, then I do not believe you would free me. I think you would leave me here. I think you plan to abandon and to betray me. I do not consent to have that ribbon placed on me."
"Fine words, and brave words," said Odin. "ords to cover your fear at being proved a coward, Fenris Wolf. You are afraid to be tied with this silken ribbon. No need for more explanations."
The wolf's tounge lolled from his mouth, and he laughed the, showing sharp teeth each the size of a human arm. "Rather than question my courage, I challenge you to prove there is no treachery planned. You can tie me up if one of you will place his hand in my mouth. I will gently close my teeth upon it, but I will not bite down. If there is no treachery afoot, I will open my mouth when I have escaped the ribbon, or when you have freed me, and his hand will be unharmed. There. I swear, if I have a hand in my mouth, you can tie me with your ribbon. So. Whose hand will it be?"

[...]

The wolf stretched and struggled; it pushed and strained every nerve and muscle to snap the ribbon that bound it. But with every struggle the task seemed harder and with every strain the glimmering ribbon became stronger.
At first the gods sniggered. Then the gods chuckled. Finally, when they were certain that the beast had been immobilised and that they were in no danger, the gods laughed.

[...]

Fenrir stopped struggling. He lay there unmoving. If the gods were going to fee him, they would do it now.
But the gods only laughed the harder.