1 Corinthians 7:10-12

10 For married people I have a command which is not my own but the Lord's: a wife must not leave her husband;

11 but if she does, she must remain single or else be reconciled to her husband; and a husband must not divorce his wife.

12 To the others I say (I, myself, not the Lord): if a Christian man has a wife who is an unbeliever and she agrees to go on living with him, he must not divorce her.