12 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. 13 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. 14 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. 15 (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.)
Matthew Henry's Commentary on 1 Corinthians 7:12-15
Commentary on 1 Corinthians 7:10-16
(Read 1 Corinthians 7:10-16)
Man and wife must not separate for any other cause than what Christ allows. Divorce, at that time, was very common among both Jews and Gentiles, on very slight pretexts. Marriage is a Divine institution; and is an engagement for life, by God's appointment. We are bound, as much as in us lies, to live peaceably with all men, Romans 12:18, therefore to promote the peace and comfort of our nearest relatives, though unbelievers. It should be the labour and study of those who are married, to make each other as easy and happy as possible. Should a Christian desert a husband or wife, when there is opportunity to give the greatest proof of love? Stay, and labour heartily for the conversion of thy relative. In every state and relation the Lord has called us to peace; and every thing should be done to promote harmony, as far as truth and holiness will permit.