May a Christian be married to an unbeliever?

The two passages deal with different situations. In 1 Corinthians 7 Paul is answering questions the Corinthians had sent him (7:1), and in verses 12–16 he speaks to people who already have an unbelieving husband or wife: “If any brother hath a wife that believeth not”. In a young church most such marriages had been made before one partner came to faith, and some apparently thought that the believer should now leave. Paul says no. The marriage stands, and the believer must not seek to end it. The unbelieving partner “is sanctified” by the believer and the children are “holy” (7:14); whatever exactly that means, and commentators differ, it shows that the marriage is not unclean and need not be ended. The believer may even win the other to Christ (7:16; compare 1 Peter 3:1).

On entering a marriage, Paul’s teaching is the same in both letters. A Christian widow is “at liberty to be married to whom she will; only in the Lord” (1 Corinthians 7:39), that is, to a fellow believer. 2 Corinthians 6:14 gives the wider rule behind this. The Greek heterozygeō means to be yoked with an animal of another kind, recalling the law “Thou shalt not plow with an ox and an ass together” (Deuteronomy 22:10). In context its first concern is idolatry (6:16), but it applies to any binding partnership, and Christians have long applied it to marriage.

The call to “come out from among them” (6:17) cannot mean that believers should leave unbelieving spouses, for Paul has expressly told them not to (1 Corinthians 7:12–13), and he has said that he never meant believers to cut themselves off from the world (1 Corinthians 5:9–10). So the teaching is consistent: do not enter a marriage with an unbeliever, but if you are already married to one, stay and be faithful.

Not only marriage

Barnes argues that 2 Corinthians 6:14 should not be confined to marriage: it forbids any close tie that would make a Christian a partner in unbelief or idolatry. On that view the rule about marriage rests chiefly on 1 Corinthians 7:39, and the conclusion is the same.

What Paul means by the unbelieving partner being ‘sanctified’ and the children ‘holy’ (1 Corinthians 7:14) is debated. Most agree that it does not mean that the unbeliever is saved, since Paul goes on to speak of the believer perhaps saving the unbelieving partner (7:16).