Sahih al-Bukhari 3550Book 61, Hadith 59
حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، قَالَ سَأَلْتُ أَنَسًا هَلْ خَضَبَ النَّبِيُّ صلى الله عليه وسلم قَالَ لاَ، إِنَّمَا كَانَ شَىْءٌ فِي صُدْغَيْهِ.
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."