(Annisa) 4 : 20
وَإِنْ أَرَدْتُمُ اسْتِبْدَالَ زَوْجٍ مَكَانَ زَوْجٍ وَآتَيْتُمْ إِحْدَاهُنَّ قِنْطَارًا فَلَا تَأْخُذُوا مِنْهُ شَيْئًا ۚ أَتَأْخُذُونَهُ بُهْتَانًا وَإِثْمًا مُبِينًا
If you wish to substitute one wife in the place of another, and if you had given one of them a heap of gold as dowry, then you shouldn’t take back anything from it; are you taking it back as slander and manifest sin?
Once in Medina, Caliph Umar on a Friday Speech wanted women to reduce their dowry to an extent that it may make it easy for the men. Hearing this a woman from the Quraish tribe questioned him quoting this verse and that who gave Umar such a right to say so which was not told by Messenger or first Caliph Aboobaker? Immediately Umar returned to the speaker chamber and revoked what he told and amended his words himself. See explanation 2: 229, 236, and 3: 144.