Sahih Muslim | Book 7 | Hadith Number 2734

Narrated by Kalb b. Ujra (Allah be pleased with him)
Kalb b. Ujra (Allah be pleased with him) reported: It was I for whom this verse was revealed (to the Holy Prophet): "Whoever among you is sick or has an ailment of the head, he (may effect) a compensation by lasting or alms or a sacrifice" He said: I came to him (the Holy Prophet) and he said: Come Dear. So I went near. He (again) said: Come near. So I went near. Thereupon the Messenger of Allah (may peace be upon him) said: Do the vermin's trouble you? Ibn Aun (one of the narrators) said: I think he (Ka'b b. Ujra) replied in the affirmative. He (the Holy Prophet) then commanded to do compensation by fasting or by giving sadaqa (feeding six needy persons) or by sacrifice (of a animal) that is available.