1 Corinthians 7:12-17

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]? Only, let each one live the life which the Lord has assigned him, and to which God has called him [for each person is unique and is accountable for his choices and conduct, let him walk in this way]. This is the rule I make in all the churches.