Hadith 4484
Chapter 12: Cheating When Trading - كتاب البيوع
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَجُلاً، ذَكَرَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم أَنَّهُ يُخْدَعُ فِي الْبَيْعِ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا بِعْتَ فَقُلْ لاَ خِلاَبَةَ " . فَكَانَ الرَّجُلُ إِذَا بَاعَ يَقُولُ لاَ خِلاَبَةَ .
It was narrated from Ibn 'Umar that:
a man told the Messenger of Allah that he was always being cheated. The Messenger of Allah said to him: "When you make a deal, say: There is no intention of cheating" So, whenever the man engages in a deal he says, 'There is no intention of cheating." "(Sahih )
Reference : Sunan an-Nasa'i 4484
In-book reference : Book 44, Hadith 36