Sahih Muslim Book 30, Hadith Number 5785.
Chapter : Pertaining to the old age of Allah’s Apostle (may peace be upon him).
Abu Juhaifa reported: I saw Allah’s Messenger (may peace be upon him) having some whiteness (in hair) at this place, and Zuhair placed one of his fingers at his chin. Juhaifa was asked how old he had been at that time. He said: I made arrows and put feathers to them (i.e. I had passed my childhood).