Yahya related to me from Malik from Abd al-Karim ibn Malik al-Jazari from Abd ar-Rahman ibn Abi Layla from Kab ibn Ujra that onetime he was with the Messenger of Allah, may Allah bless him and granthim peace, in ihram, and he was suffering from lice on his head. TheMessenger of Allah, may Allah bless him and grant him peace, told himto shave his head, saying, "Fast three days, or feed six poor people,two mudds for each person, or sacrifice a sheep. If you do any ofthose it will be enough for you."
USC-MSA web (English) reference: Book 20, Hadith 246
Arabic reference: Book 20, Hadith 943