Sahih Muslim
The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His Companions (Kitab Al-Fadail)
Book Number: 030 / Hadith Number: 5750
Anas reported: I saw when the Messenger of Allah (may peace be upon him) got his hair cut by the barber, his Companions came round him and they eagerly wanted that no hair should fall but in the hand of a person.