An-Nisa' 4:20

وَإِنْ أَرَدتُّمُ ٱسْتِبْدَالَ زَوْجٍۢ مَّكَانَ زَوْجٍۢ وَءَاتَيْتُمْ إِحْدَىٰهُنَّ قِنطَارًۭا فَلَا تَأْخُذُوا۟ مِنْهُ شَيْـًٔا ۚ أَتَأْخُذُونَهُۥ بُهْتَٰنًۭا وَإِثْمًۭا مُّبِينًۭا

But if ye decide to take one wife in place of another, even if ye had given the latter a whole treasure for dower, Take not the least bit of it back: Would ye take it by slander and manifest wrong?