It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) shaved his blessed head during the Farewell Hajj. Ibn Umar said: The people used to shave their heads during Hajj and then perform Umrah at the time of departure, and they would ask: "With what should this be shaved?" So we would say: "Have the razor passed over your head." This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it!