Verses 19-21 of Chapter 4:

O Believers, it is not lawful for you to become the heirs of widows by force: nor is it lawful that you should treat your wives harshly in order to deprive them of a part of the dowry you have given them. However (you have the right to treat them harshly), if they are guilty of adultery. You should live with them in an honorable manner, even if you dislike them; it is possible that Allah may bring much good to you through that very thing you dislike. And if you make up your mind to marry another wife in place of the one you already have, do not take back anything out of what you have given her. even though it may have been a heap of wealth. Will you take it back by slander and gross injustice? And how is it proper for you to take it, when both of you have enjoyed conjugal happiness and she received from you a solemn pledge of union?