The Book of Pilgrimage (Kitab Al-Hajj)
Muslim :: Book 7 : Hadith 2734
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 ail- ment 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 Iwent near. He (again) said: Come near. So I went near. Thereupon the Messenger of Allah (may peace be upon him) said: Do the vermins 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 @adaqa (feed- ing six needy persons) or by sacrifice (of a animal) that is available.