Sahih al-Bukhari 2176
صحيح البخاري#2176SahihNarrated Abu Sa`id:(Concerning exchange) that he heard Allah's Messenger (ﷺ) saying, "Do not sell gold for gold unless equal in weight, and do not sell silver unless equal in weight
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: 34:126