4:19

O believers! It is not lawful for you consider women as a part of your inheritance and retain them against their will in order that you may force them to give up a part of the dowry you have given them, unless they are guilty of proven fornication. Treat them with kindness even if you dislike them; it is quite possible that you dislike something in which Allah has placed much good.
Meaning:-
Fornication: sexual intercourse between people not married to each other.