It is narrated from Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) that he said: The vermin (lice) of my head troubled me, so I came to the Messenger of Allah (peace and blessings be upon him) and asked him about it. Then Allah, the Mighty and Majestic, revealed this verse: "And whoever among you is ill or has an ailment of the head, then (he must offer) a ransom of fasting, or charity, or sacrifice" [Surah al-Baqarah: 196]. Then the Messenger of Allah (peace and blessings be upon him) called me and said: "Do you have a faraq that you can distribute among six poor people" and a faraq equals three sa' "or the sacrifice of a sheep, or will you fast three days?" I said: O Messenger of Allah, choose for me. He (peace and blessings be upon him) said: "Feed six poor people."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16398