Sahih al-Bukhari — Loans, Payment of Loans, Freezing of Property, Bankruptcy — Hadith No: 2407
Translation
Narrated Ibn `Umar:A man came to the Prophet (ﷺ) and said, "I am often betrayed in bargaining." The Prophet (ﷺ) advised him, "When you buy something, say (to the seller), 'No deception." The man used to say so afterwards