4:20 · An-Nisaa
وَإِنْ أَرَدْتُمُ اسْتِبْدَالَ زَوْجٍ مَكَانَ زَوْجٍ وَآتَيْتُمْ إِحْدَاهُنَّ قِنْطَارًا فَلَا تَأْخُذُوا مِنْهُ شَيْئًا ۚ أَتَأْخُذُونَهُ بُهْتَانًا وَإِثْمًا مُبِينًا
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?