1 Corinthians 7:12-17

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. And if a believing woman has a husband who is not a believer and he is willing to continue living with her, she must not leave him. For the believing wife brings holiness to her marriage, and the believing husband brings holiness to his marriage. Otherwise, your children would not be holy, but now they are holy. (But if the husband or wife who isn’t a believer insists on leaving, let them go. In such cases the believing husband or wife is no longer bound to the other, for God has called you to live in peace.) Don’t you wives realize that your husbands might be saved because of you? And don’t you husbands realize that your wives might be saved because of you? Each of you should continue to live in whatever situation the Lord has placed you, and remain as you were when God first called you. This is my rule for all the churches.