Sahih Bukhari

Narrated Ka`b bin 'Ujra:I came to the Prophet (ﷺ) and he said to me, ""Come near."" So I went near to him and he said, ""Are your lice troubling you?"" I replied, ""Yes."" He said, ""(Shave your head and) make expiation in the form of fasting, Sadaqa (giving in charity), or offering a sacrifice."" (The sub-narrator) Aiyub said, ""Fasting should be for three days, and the Nusuk (sacrifice) is to be a sheep, and the Sadaqa is to be given to six poor persons