It was narrated from Ibn 'Umar that the Messenger of Allah said:

"Do not urge someone to cancel a sale he has already agreed upon so as to sell him your own goods, unless he bys or changes his mind."

أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا أَبُو مُعَاوِيَةَ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ رَسُولِ اللَّهِ ﷺ قَالَ " لاَ يَبِيعُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ حَتَّى يَبْتَاعَ أَوْ يَذَرَ " .