1 Corinthians 7:11-12

11But if she does leave him, she must not marry another man. Or she should go back to live with her husband. In the same way, a husband must not send his wife away.

12To all you other people, I say this. (This is what I think. The Lord has not spoken about it.) A Christian man may have a wife who does not believe in Christ. If she agrees to continue living with him, then he should not send her away.