1Cor 7:8-16
Now to the unmarried and to widows I say: it is a good thing for them to remain as they are, as I do, but if they cannot exercise self-control they should marry, for it is better to marry than to be on fire. To the married, however, I give this instruction (not I, but the Lord): A wife should not separate from her husband —and if she does separate she must either remain single or become reconciled to her husband—and a husband should not divorce his wife.
To the rest I say (not the Lord): if any brother has a wife who is an unbeliever, and she is willing to go on living with him, he should not divorce her; and if any woman has a husband who is an unbeliever, and he is willing to go on living with her, she should not divorce her husband. For the unbelieving husband is made holy through his wife, and the unbelieving wife is made holy through the brother. Otherwise your children would be unclean, whereas in fact they are holy.
If the unbeliever separates, however, let him separate