(7) باب مَا يُنْهَى مِنَ الْخِدَاعِ فِي الْبُيُوعِ
Narrated `Abdullah bin `Umar:
A man mentioned to the Prophet (ﷺ) that he had always been cheated in bargains. The Prophet (ﷺ) said, "Whenever you do bargain, say, 'No cheating.'"
Reference: Sahih al-Bukhari 6964
In-book reference: Book 90, Hadith 11
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 86, Hadith 94