Sahih al-Bukhari 2723
Sahih al-Bukhari · Book 54: Conditions · The conditions not permissible in marriage contracts
Narrated Abu Huraira:
حَدَّثَنَا مُسَدَّدٌ ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ ، حَدَّثَنَا مَعْمَرٌ ، عَنِ الزُّهْرِيِّ ، عَنْ سَعِيدٍ ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " لاَ يَبِيعُ حَاضِرٌ لِبَادٍ، وَلاَ تَنَاجَشُوا، وَلاَ يَزِيدَنَّ عَلَى بَيْعِ أَخِيهِ، وَلاَ يَخْطُبَنَّ عَلَى خِطْبَتِهِ، وَلاَ تَسْأَلِ الْمَرْأَةُ طَلاَقَ أُخْتِهَا لِتَسْتَكْفِئَ إِنَاءَهَا " .
The Prophet (ﷺ) said, "No town-dweller should sell for a bedouin. Do not practice Najsh (i.e. Do not offer a high price for a thing which you do not want to buy, in order to deceive the people). No Muslim should offer more for a thing already bought by his Muslim brother, nor should he demand the hand of a girl already engaged to another Muslim. A Muslim woman shall not try to bring about The divorce of her sister (i.e. another Muslim woman) in order to take her place herself."