Narrated Thabit:

Anas was asked whether the Prophet used a a hair dye or not. Anas replied, "The Prophet had not enough grey hair to dye. I could even count the white grey hairs oil his beard ill would."

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ ثَابِتٍ، قَالَ سُئِلَ أَنَسٌ عَنْ خِضَابِ النَّبِيِّ، ﷺ فَقَالَ إِنَّهُ لَمْ يَبْلُغْ مَا يَخْضِبُ، لَوْ شِئْتُ أَنْ أَعُدَّ شَمَطَاتِهِ فِي لِحْيَتِهِ.