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.  

أَنَّ رَجُلاً ذَكَرَ لِرَسُولِ اللَّهِ ﷺ أَنَّهُ يُخْدَعُ فِي الْبَيْعِ فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ إِذَا بَايَعْتَ فَقُلْ لاَ خِلاَبَةَ فَكَانَ الرَّجُلُ إِذَا بَايَعَ يَقُولُ لاَ خِلاَبَةَ  

During the time of the Messenger of Allah ﷺ a man used to buy (goods), and he was weak in his intellect. His people came to the Prophet of Allah ﷺ and said: Prophet of Allah, stop so-and-so (to make a bargain) for he buys (goods), but he is weak in his intellect. So the Prophet ﷺ called on him and forbade him to make a bargain. He said: Prophet of Allah, I cannot keep away myself from business transactions. Thereupon the Messenger of Allah ﷺ said: If you cannot give up making a bargain , then say: Take , and give, and there is no attempt to deceive.  

أَنَّ رَجُلاً عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ كَانَ يَبْتَاعُ وَفِي عُقْدَتِهِ ضَعْفٌ فَأَتَى أَهْلُهُ نَبِيَّ اللَّهِ ﷺ فَقَالُوا يَا نَبِيَّ اللَّهِ احْجُرْ عَلَى فُلاَنٍ فَإِنَّهُ يَبْتَاعُ وَفِي عُقْدَتِهِ ضَعْفٌ فَدَعَاهُ النَّبِيُّ ﷺ فَنَهَاهُ عَنِ الْبَيْعِ فَقَالَ يَا نَبِيَّ اللَّهِ إِنِّي لاَ أَصْبِرُ عَنِ الْبَيْعِ فَقَالَ رَسُولُ اللَّهِ ﷺ إِنْ كُنْتَ غَيْرَ تَارِكٍ الْبَيْعَ فَقُلْ هَاءَ وَهَاءَ وَلاَ خِلاَبَةَ قَالَ أَبُو ثَوْرٍ عَنْ سَعِيدٍ