Messenger of Allah ﷺ said, "Do not urge somebody to return what he has already bought (i.e. in optional sale) from another seller so as to sell him your own goods."  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَبِيعُ بَعْضُكُمْ عَلَى بَيْعِ أَخِيهِ  

Messenger of Allah ﷺ forbade the selling of things by a town dweller on behalf of a desert dweller; and similarly Najsh was forbidden. And one should not urge somebody to return the goods to the seller so as to sell him his own goods; nor should one demand the hand of a girl who has already been engaged to someone else; and a woman should not try to cause some other woman to be divorced in order to take her place.  

نَهَى رَسُولُ اللَّهِ ﷺ أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ وَلاَ تَنَاجَشُوا وَلاَ يَبِيعُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبُ عَلَى خِطْبَةِ أَخِيهِ وَلاَ تَسْأَلُ الْمَرْأَةُ طَلاَقَ أُخْتِهَا لِتَكْفَأَ مَا فِي إِنَائِهَا