Sahih Muslim 2341 b
Ibn Sirin reported:
I asked Anas b. Malik whether Allah's Messenger (ﷺ) dyed his hair. He said: He had not reached the stage when (he needed) dyeing (of his white hair). He had a few white hair in his beard. I said to him: Did Abu Bakr dye his hair? He said: Yes, with hina' (henna).
حَدَّثَنَا مُحَمَّدُ بْنُ بَكَّارِ بْنِ الرَّيَّانِ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ زَكَرِيَّاءَ، عَنْ عَاصِمٍ الأَحْوَلِ،
 عَنِ ابْنِ سِيرِينَ، قَالَ سَأَلْتُ أَنَسَ بْنَ مَالِكٍ هَلْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم خَضَبَ
 فَقَالَ لَمْ يَبْلُغِ الْخِضَابَ كَانَ فِي لِحْيَتِهِ شَعَرَاتٌ بِيضٌ ‏.‏ قَالَ قُلْتُ لَهُ أَكَانَ أَبُو بَكْرٍ يَخْضِبُ
 قَالَ فَقَالَ نَعَمْ بِالْحِنَّاءِ وَالْكَتَمِ ‏.‏