Quran 4:21 — Women (Al-Nesa')

وَكَيفَ تَأخُذونَهُ وَقَد أَفضىٰ بَعضُكُم إِلىٰ بَعضٍ وَأَخَذنَ مِنكُم ميثٰقًا غَليظًا

How could you take it back, after you have been intimate with each other, and they had taken from you a solemn pledge?

[4:20] If you wish to marry another wife, in place of your present wife, and you had given any of them a great deal, you shall not take back anything you had given her. Would you take it fraudulently, maliciously, and sinfully?

[4:22] Do not marry the women who were previously married to your fathers—existing marriages are exempted and shall not be broken—for it is a gross offense, and an abominable act.