there was a man at the time of the Messenger of Allah ﷺ whose mental faculties were lacking, and he used to buy and sell. His family came to the Prophet ﷺ and said, “O Messenger of Allah, stop him.” So The Prophet ﷺ called him, and told him not to do that. He said: “O Messenger of Allah ﷺ, I cannot bear to be away from business.” He said, “If you engage in a transaction then say: “Take it (i.e., the goods) and don't cheat (me).' ”  

أَنَّ رَجُلاً كَانَ فِي عَهْدِ رَسُولِ اللَّهِ ﷺ فِي عُقْدَتِهِ ضَعْفٌ وَكَانَ يُبَايِعُ وَأَنَّ أَهْلَهُ أَتَوُا النَّبِيَّ ﷺ فَقَالُوا يَا رَسُولَ اللَّهِ احْجُرْ عَلَيْهِ فَدَعَاهُ النَّبِيُّ ﷺ فَنَهَاهُ عَنْ ذَلِكَ فَقَالَ يَا رَسُولَ اللَّهِ إِنِّي لاَ أَصْبِرُ عَنِ الْبَيْعِ فَقَالَ إِذَا بَايَعْتَ فَقُلْ هَا وَلاَ خِلاَبَةَ  

“My grandfather was Munqidh bin 'Amr. He was a man who had suffered a head wound and lost the power of speech, but that did not stop him from engaging in trade. He was always being cheated, so he went to the Prophet ﷺ and told him about that. He said to him: 'When you buy something, say: “There should be no intention of cheating,” and for every product you buy, you have the choice for three nights. If you are pleased with it, keep it, and if you are displeased then return it.'”  

هُوَ جَدِّي مُنْقِذُ بْنُ عَمْرٍو وَكَانَ رَجُلاً قَدْ أَصَابَتْهُ آمَّةٌ فِي رَأْسِهِ فَكَسَرَتْ لِسَانَهُ وَكَانَ لاَ يَدَعُ عَلَى ذَلِكَ التِّجَارَةَ وَكَانَ لاَ يَزَالُ يُغْبَنُ فَأَتَى النَّبِيَّ ﷺ فَذَكَرَ ذَلِكَ لَهُ فَقَالَ لَهُ إِذَا أَنْتَ بَايَعْتَ فَقُلْ لاَ خِلاَبَةَ ثُمَّ أَنْتَ فِي كُلِّ سِلْعَةٍ ابْتَعْتَهَا بِالْخِيَارِ ثَلاَثَ لَيَالٍ فَإِنْ رَضِيتَ فَأَمْسِكْ وَإِنْ سَخِطْتَ فَارْدُدْهَا عَلَى صَاحِبِهَا