1 Corinthians 7:10-16

But to the married [believers] I give instructions—not I, but the Lord—that the wife is not to separate from her husband, (but even if she does leave him, let her remain single or else be reconciled to her husband) and that the husband should not leave his wife. To the rest I declare—I, not the Lord [since Jesus did not discuss this]—that if any [believing] brother has a wife who does not believe [in Christ], and she consents to live with him, he must not leave her. And if any [believing] woman has an unbelieving husband, and he consents to live with her, she must not leave him. For the unbelieving husband is sanctified [that is, he receives the blessings granted] through his [Christian] wife, and the unbelieving wife is sanctified through her believing husband. Otherwise your children would be [ceremonially] unclean, but as it is they are holy. But if the unbelieving partner leaves, let him leave. In such cases the [remaining] brother or sister is not [spiritually or morally] bound. But God has called us to peace. For how do you know, wife, whether you will save your husband [by leading him to Christ]? Or how do you know, husband, whether you will save your wife [by leading her to Christ]?