1 Corinthians 7:10-12

But for those who are married, I have a command that comes not from me, but from the Lord. A wife must not leave her husband. But if she does leave him, let her remain single or else be reconciled to him. And the husband must not leave his wife. Now, I will speak to the rest of you, though I do not have a direct command from the Lord. If a fellow believer has a wife who is not a believer and she is willing to continue living with him, he must not leave her.