What was the Prophet Muhammad's (peace be upon him) advice to Ka`b bin Ujra when he noticed the lice falling on his face?
 Narrated Ka`b bin Ujra:                     The Prophet came to me at the time of Al-Hudaibiya Pledge while lice were falling on my face. He said, "Are the lice of your head troubling you?" I said, "Yes." He said, "Shave your head and fast for three days, or feed six poor persons, or slaughter a sheep as sacrifice." (The sub-narrator, Aiyub said, "I do not know with which of these three options he started.")