Sahih al-Bukhari 5899
صحيح البخاري#5899SahihNarrated Abu Huraira:The Prophet (ﷺ) said, "Jews and Christians do not dye their hair so you should do the opposite of what they do
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 77:116