Sahih al-Bukhari 3920
صحيح البخاري#3920SahihThrough another group of narrators, Anas bin Malik said: "When the Prophet (ﷺ) 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
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: 63:145