Sahih al-Bukhari 6756
صحيح البخاري#6756SahihNarrated Ibn `Umar:The Prophet (ﷺ) forbade the selling of the Wala' (of slaves) or giving it as a present
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: 85:33