Sahih al-Bukhari, Book 63, Hadith 146 (In-Book) ⓘ
Through another group of narrators, Anas bin Malik said: "When the Prophet arrived at Medina, the eldest amongst his companions was Abu Bakr. He dyed his hair with Hinna and Katam till it became of dark red color.
وَقَالَ دُحَيْمٌ حَدَّثَنَا الْوَلِيدُ، حَدَّثَنَا الأَوْزَاعِيُّ، حَدَّثَنِي أَبُو عُبَيْدٍ، عَنْ عُقْبَةَ بْنِ وَسَّاجٍ، حَدَّثَنِي أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ قَالَ قَدِمَ النَّبِيُّ صلى الله عليه وسلم الْمَدِينَةَ، فَكَانَ أَسَنَّ أَصْحَابِهِ أَبُو بَكْرٍ، فَغَلَفَهَا بِالْحِنَّاءِ وَالْكَتَمِ حَتَّى قَنَأَ لَوْنُهَا.
also referenced under: Hadith 3920 (DarusSalam) & Volume 5, Book 58, Hadith 257 (USC-MSA)