Sunan Ibn Majah 2354
It was narrated from Anas bin Malik that :
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).' ”
حَدَّثَنَا أَزْهَرُ بْنُ مَرْوَانَ، حَدَّثَنَا عَبْدُ الأَعْلَى، حَدَّثَنَا سَعِيدٌ، عَنْ قَتَادَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ رَجُلاً، كَانَ فِي عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي عُقْدَتِهِ ضَعْفٌ وَكَانَ يُبَايِعُ وَأَنَّ أَهْلَهُ أَتَوُا النَّبِيَّ صلى الله عليه وسلم فَقَالُوا يَا رَسُولَ اللَّهِ احْجُرْ عَلَيْهِ ‏.‏ فَدَعَاهُ النَّبِيُّ صلى الله عليه وسلم فَنَهَاهُ عَنْ ذَلِكَ فَقَالَ يَا رَسُولَ اللَّهِ إِنِّي لاَ أَصْبِرُ عَنِ الْبَيْعِ ‏.‏ فَقَالَ ‏
"‏ إِذَا بَايَعْتَ فَقُلْ هَا وَلاَ خِلاَبَةَ ‏"‏ ‏.‏