Sahih al-Bukhari 2414
صحيح البخاري#2414SahihNarrated Ibn `Umar:A man was often cheated in buying. The Prophet (ﷺ) said to him, "When you buy something, say (to the seller), No cheating." The man used to say so thenceforward
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: 44:5