Sahih Bukhari Volume 4, Book 61, Hadith 3550

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكُ بْنُ أَنَسٍ، عَنْ رَبِيعَةَ بْنِ أَبِي عَبْدِ الرَّحْمَنِ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ أَنَّهُ سَمِعَهُ يَقُولُ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم لَيْسَ بِالطَّوِيلِ الْبَائِنِ وَلاَ بِالْقَصِيرِ، وَلاَ بِالأَبْيَضِ الأَمْهَقِ، وَلَيْسَ بِالآدَمِ وَلَيْسَ بِالْجَعْدِ الْقَطَطِ وَلاَ بِالسَّبْطِ، بَعَثَهُ اللَّهُ عَلَى رَأْسِ أَرْبَعِينَ سَنَةً، فَأَقَامَ بِمَكَّةَ عَشْرَ سِنِينَ، وَبِالْمَدِينَةِ عَشْرَ سِنِينَ، فَتَوَفَّاهُ اللَّهُ، وَلَيْسَ فِي رَأْسِهِ وَلِحْيَتِهِ عِشْرُونَ شَعْرَةً بَيْضَاءَ‏.‏

Narrated By 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.