Virtues and Merits of the Prophet (pbuh) and his Companions
حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، قَالَ سَأَلْتُ أَنَسًا هَلْ خَضَبَ النَّبِيُّ صلى الله عليه وسلم قَالَ لاَ، إِنَّمَا كَانَ شَىْءٌ فِي صُدْغَيْهِ.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
From Sahih al-Bukhari, whose reports the scholars accept as authentic.