Sunan Abi Dawud 4209
سنن أبي داود#4209Sahihحَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، حَدَّثَنَا حَمَّادٌ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، أَنَّهُ سُئِلَ عَنْ خِضَابِ النَّبِيِّ، صلى الله عليه وسلم فَذَكَرَ أَنَّهُ لَمْ يَخْضِبْ وَلَكِنْ قَدْ خَضَبَ أَبُو بَكْرٍ وَعُمَرُ رَضِيَ اللَّهُ عَنْهُمَا .
Thabit said that Anas was asked about the hair-dye of the Prophet (ﷺ). He replied:He did not dye his hair, but Abu Bakr and 'Umar dyed their hair
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Bukhari (5895) Sahih Muslim (2341)
In-book reference: 35:51