Abd al-Rahman bin Abi Layla (may Allah have mercy on him) narrates from Ka'b bin Ujrah (may Allah be pleased with him) that this verse was revealed about me: I came to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Come closer." I came closer two or three times, and he (peace and blessings be upon him) asked: "Are your lice troubling you?" I think he said: "Yes."
(b) Ayyub reports these words from Mujahid: "Have the lice of your head troubled you?" Then he (peace and blessings be upon him) ordered me to fast, give charity or offer a sacrifice, whichever was easy. Ibn Awn said: Mujahid had explained it to me, but I forgot. Ayyub informed me that he heard from Mujahid: fasting three days, or charity to six poor people, or the sacrifice of a goat.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9793
Abd al-Rahman bin Abi Layla narrates from Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) that he was with the Prophet (peace and blessings be upon him) in the state of ihram, and lice troubled him. So the Messenger of Allah (peace and blessings be upon him) ordered him to shave his head and said: "Fast three days, or give six poor people two mudd of food each, or sacrifice a goat; whichever of these you do will suffice for you."
This is the correct (chain). Malik also narrated it on another occasion from Abd al-Karim al-Jazari, from Abd al-Rahman bin Abi Layla, without mentioning Mujahid in its chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9794
Abd al-Rahman bin Abi Layla (may Allah have mercy on him) narrates from Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him), and in it is: "three sa' of dates."
(b) Al-Hakam bin Utaybah (may Allah have mercy on him) narrates from Abd al-Rahman (may Allah have mercy on him): "one faraq (a measure) of raisins."
(c) Abdullah bin Ma'qil (may Allah have mercy on him) narrates from Sayyiduna Ka'b (may Allah be pleased with him): "for each poor person half a sa' of food."
Al-Shafi'i said: Malik erred in this hadith (by omitting Mujahid); the hadith masters preserved it from Abd al-Karim, from Mujahid, from Abd al-Rahman bin Abi Layla, from Ka'b bin Ujrah. The Shaykh said: He erred in this only in some of the presentations (of al-Muwatta), and in some of them he narrated it correctly.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9795