It is narrated from Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said to him, while the lice of his head were troubling him: "Slaughter a nusuk (sacrifice), or fast three days, or give three sa' in charity to six poor people."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16302