An-Nisa 4:20

وَإِنۡ أَرَدتُّمُ ٱسۡتِبۡدَالَ زَوۡجٖ مَّكَانَ زَوۡجٖ وَءَاتَيۡتُمۡ إِحۡدَىٰهُنَّ قِنطَارٗا فَلَا تَأۡخُذُواْ مِنۡهُ شَيۡـًٔاۚ أَتَأۡخُذُونَهُۥ بُهۡتَٰنٗا وَإِثۡمٗا مُّبِينٗا 20

But if you want to replace one wife with another and you have given one of them a great amount [in gifts], do not take [back] from it anything. Would you take it in injustice and manifest sin