Sahih Bukhari | Volume 4 | Hadith Number 747
Narrated by Rabia bin Abi Abdur-Rahman
I heard Anas bin Malik describing the Prophet saying, "He was of medium height amongst the people, neither tall nor short; he had a rosy colour, neither absolutely white nor deep brown; his hair was neither completely curly nor quite lank. Divine Inspiration was revealed to him when he was forty years old. He stayed ten years in Mecca receiving the Divine Inspiration, and stayed in Medina for ten more years. When he expired, he had scarcely twenty white hairs in his head and beard." Rabi'a said, "I saw some of his hairs and it was red. When I asked about that, I was told that it turned red because of scent."