Virtues and Merits of the Prophet (pbuh) and his Companions

Bukhari :: Book 4 :: Volume 56 :: Hadith 748

Narrated Anas:

Allah's Apostle was neither very tall nor short, neither absolutely white nor deep brown. His hair was neither curly nor lank. Allah sent him (as an Apostle) when he was forty years old. Afterwards he resided in Mecca for ten years and in Medina for ten more years. When Allah took him unto Him, there was scarcely twenty white hairs in his head and beard.