It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said to Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him): "Perhaps the lice of your head have troubled you?" He said: Yes, O Messenger of Allah. He (peace and blessings be upon him) said: "Shave your head, and offer a cow as a sacrifice, marking its hump or hanging a garland around its neck."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16259
It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) shaved his head, and the Messenger of Allah (peace and blessings be upon him) ordered him to give a ransom (fidyah), so he gave a cow as ransom.
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16260