Sahih al-Bukhari, Volume 4, Book 56, Hadith 750 (USC-MSA) ⓘ
Narrated Qatada: I asked Anas, "Did the Prophet 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.
also referenced under: Book 61, Hadith 59 (In-Book) & Hadith 3550 (DarusSalam)