Hadith 625:28
Yahya narrated to us, from Sayf, who said: I heard Mujahid saying: Ibn Abi Layla narrated to me, saying: Ka’b ibn ‘Ujrah narrated to me, that the Prophet, peace and blessings of Allah be upon him, stopped by him at al-Hudaybiyyah. He said: And his head was falling with lice. He said: "Do your vermin bother you?" He said: I said: Yes. He said: "Then shave your head." He said: Regarding me was revealed: {And whoever among you is ill or has an ailment of the head [making shaving necessary], then an expiation of fasting [three days] or charity or sacrifice} [Al-Baqarah: 196]. He said: So the Messenger of Allah, peace and blessings of Allah be upon him, commanded me and said: "Fast three days, or give in charity a *faraq* [a measure] between six [poor people], or [offer] a sacrifice of what is easy."
حدثنا يحيى، عن سيف، قال: سمعت مجاهدا، يقول: حدثني ابن أبي ليلى، قال: حدثني كعب بن عجرة، أن النبي صلى الله عليه وسلم، وقف عليه بالحديبية، قال: ورأسه يتهافت قملا، قال: " أيؤذيك هوامك "؟ قال: قلت: نعم، قال: " فاحلق رأسك " قال: في نزلت {فمن كان منكم مريضا، أو به أذى من رأسه، ففدية من صيام، أو صدقة، أو نسك} [البقرة: 196] قال: فأمرني رسول الله صلى الله عليه وسلم، فقال: " صم ثلاثة أيام، أو تصدق بفرق بين ستة، أو بنسك ما تيسر "