A man told the Messenger of Allah ﷺ that he was being deceived in business transactions. The Messenger of Allah ﷺ then said: When you make a bargain, say: There is no attempt to deceive. So when the man made a bargain, he said: There is no attempt to deceive. (Using translation from Abū Dāʾūd 3500)  

أَنَّ رَجُلًا ذَكَرَ لِرَسُولِ اللهِ ﷺ أَنَّهُ يُخْدَعُ فِي الْبَيْعِ فَقَالَ لَهُ رَسُولُ اللهِ ﷺ إِذَا بَايَعْتَ فَقُلْ لَا خِلَابَةَ وَكَانَ الرَّجُلُ إِذَا بَاعَ يَقُولُ لَا خِلَابَةَ  

there was a man whose mental faculties were lacking, and he used to buy and sell. His family came to the Prophet and said: "O Prophet of Allah stop him." So the Prophet of Allah called him, and told him not to do that. He said: "O Prophet of Allah, I cannot bear to be away from business," He said "If you engaged in a deal then say: 'There is no intention to deceive. "' (Sahih ) (Using translation from Nasāʾī 4485)   

وَأَنَّ أَهْلَهُ أَتَوَا النَّبِيَّ ﷺ فَقَالُوا يَا نَبِيَّ اللهِ احْجُرْ عَلَيْهِ فَدَعَاهُ نَبِيُّ اللهِ ﷺ فَنَهَاهُ فَقَالَ يَا نَبِيَّ اللهِ إِنِّي لَا أَصْبِرُ عَنِ الْبَيْعِ قَالَ إِذَا بِعْتَ فَقُلْ لَا خِلَابَةَ