Sahih Muslim 5509
صحيح مسلم#5509SahihJabir b. 'Abdullah reported that Abu Qubafa was led (to the andience of the Holy Prophet) on the day of the Conquest of Mecca and his head and beard were white like hyssop, whereupon Allah's Messenger (ﷺ) said:Change it with something but avoid black
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 37:124