Language:
كتاب المناقب
61  
Virtues and Merits of the Prophet (pbuh) and his Companions
(23)
Chapter: The description of the Prophet (saws)
(23)
باب صِفَةِ النَّبِيِّ صلى الله عليه وسلم
Sahih al-Bukhari 3550

Narrated Qatada:

I asked Anas, "Did the Prophet (ﷺ) use to dye (his) hair?" He said, "No, for there were only a few white hairs on his temples."

حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، قَالَ سَأَلْتُ أَنَسًا هَلْ خَضَبَ النَّبِيُّ صلى الله عليه وسلم قَالَ لاَ، إِنَّمَا كَانَ شَىْءٌ فِي صُدْغَيْهِ‏.‏
Reference : Sahih al-Bukhari 3550
In-book reference : Book 61, Hadith 59
USC-MSA web (English) reference : Vol. 4, Book 56, Hadith 750
  (deprecated numbering scheme)