1 Corinthians 7:17

Only, as the Lord hath distributed to each man, as God hath called each, so let him walk. And so ordain I in all the churches. [Paul first answers generally that under no conditions are the husband and wife to separate (the single exception (Matthew 19:9) not being given, because not a point in controversy). This law, however, rests not on Paul's authority alone (which some of the Judaizers might question), but on that of the Lord himself, who plainly propounded it, repealing the ordinances of Moses which were contrary to it (see "Fourfold Gospel," p. 242). As an inspired apostle, Paul applies this law to the case of Christians united in wedlock with unbelievers, and declares that such should not separate on account of their faith; for the law of Christ so reverses that of Moses that the Christian sanctifies or removes the uncleanness of the unbelieving partner, and of the children. But such unequal marriages are not favored by God (2 Corinthians 6:14), and therefore if the unbeliever be so intolerant as to refuse to live with a converted partner, then the partner is not under bondage to the unbeliever. But God calls the believer to a life of peace which forbids any such discordant acts as tend to induce or drive the unbeliever to dissolve the marriage, for by the exercise of Christian gentleness and forbearance the believer may convert and save the unbeliever (1 Peter 3:1-2). As a summary rule for all things of a smaller nature, the apostle says that each man must rest content to walk in the lot which God has apportioned to him, not making his new religion an excuse for unwarranted changes. As this rule applied to all churches, it worked no especial hardship to the Corinthians.]