In 2 Corinthians 6:14-16 six words are used interchangeably: heterozugéō (unequally yoked or matched; bound together), metochē (a sharing, partaking; partnership), koinōnía (communion, fellowship), sumphōnēsis (unison, agreement, concord, harmony), merís (a portion in common, a share), and sugkatáthesis (agreement, assent, accord, alliance). With these synonyms in mind, it is apparent that more than mere “external association” is involved here. These relationships have agreement, unity of mind and purpose, and certain things in common. Paul is not simply addressing physical union or calling for spatial separation (“since then you would need to go out of the world,” 1 Cor. 5:9-13; cf. 7:12-13; 10:27), but the focus is on spiritual, mental, and participatory alliance (cf. Col. 3:2; 1 John 2:15).
The metaphor “unequally yoked” may have been borrowed from Deut. 22:10, “You shall not plow with an ox and a donkey together.” Not only is a close relationship indicated, but Paul’s usage would apply to the binding together of beliefs, priorities, pursuits, activities, et al.1 He is forbidding unholy alliances with the unbelieving world.
The reason given is a list of contrasting opposites: “righteousness” vs. “lawlessness”; “light” vs. “darkness”; “Christ” vs. “Belial” [Satan]; “believing ones” vs. “unbelieving ones”; “temple of God” vs. “idols.” Everything contrasted here with Christian values is peculiar to the unbelieving world, particularly mid-first-century Corinth, from which believers are to be cognitively and behaviorally separated. The Christians of Corinth are being reminded to make a complete break, not with all their associations in the world (cf. 1 Cor. 5:9-10; 7:13-14; 10:27; 14:23), but with their idolatrous and sinful past (cf. 1 Cor. 6:18; 10:7, 14).
How, then, does “unequally yoked” apply to marriage? While I am a strong advocate of faithful Christians marrying only faithful Christians (cf. 1 Cor. 7:39; 9:5), this is not what is specifically being addressed here. I would argue that it is extremely unwise for a child of God to marry an unbeliever, and I would counsel against it. As a disciple of Jesus, why would I want to spend my life with someone with whom I won't spend eternity? Why would I choose to marry a person with whom I can’t pray? Why would I intentionally prearrange for my children to grow up in a religiously divided home and likely be influenced to take the wrong spiritual path? Why would I purposefully marry someone knowing we probably won’t be going to church together and certainly not serving the Lord together?
However, what happens when a believer marries an unbeliever anyway? Paul has already affirmed to the Corinthians that a marriage involving a Christian and a non-Christian, though less than ideal, is sanctioned by God and must not be dissolved (1 Cor. 7:10-14;2 cf. Matt. 19:6). Therefore, if 2 Cor. 6:14-18 is to be applied to a religiously-mixed marriage, it would mean that the Christian wife or husband must not be in agreement with or participate in the sinful behavior of the non-Christian husband or wife. Leading one’s spouse to Christ should then be a top priority (1 Cor. 7:16; 1 Pet. 3:1-2).
--Kevin L. Moore
1 Contextually, because of the strained relationship between the Corinthians on one hand, and Paul and his associates on the other (vv. 11-13), the readers are being encouraged to correct their attitudes and behavior and to restore unity with God’s faithful ones.2 Those who argue that 1 Cor. 7:12-14 is directed only to couples already married are making an assumption not explicit in the text. If a believer goes ahead and marries an unbeliever anyway, would these directives still apply? Would it be sinful to enter into such a union but not sinful to remain in such a union? This is similar to the casuistic or case law (“if … then”) in 1 Cor. 7:10-11, where the order is not to separate or divorce (v. 10), but if this happens anyway, the Lord still has certain expectations (v. 11).