(58) باب لاَ يَبِيعُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَسُومُ عَلَى سَوْمِ أَخِيهِ، حَتَّى يَأْذَنَ لَهُ أَوْ يَتْرُكَ
Narrated Abu Huraira:
Allah's Messenger (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.
Reference: Sahih al-Bukhari 2140
In-book reference: Book 34, Hadith 92
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 34, Hadith 350