What does 2 Corinthians 6:14 mean?
Paul has just urged the Corinthians to open their hearts to him again. Now he turns to a direct command: that believers in Christ not be yoked with unbelievers. The imagery of the "yoke" brings to mind the rigid harness used to keep livestock locked together and pulling in a consistent direction. The Old Testament used a form of the word to forbid mating cattle of different species (Leviticus 19:19). The Law also forbids harnessing together an ox and a donkey to plow a field (Deuteronomy 22:10).The point of this phrase will soon become clear. Those in Christ are something other than those who are not in Christ. They are not the same—spiritually—and should not be locked together into any kind of binding relationship. Paul begins to ask a series of questions to show the absurdity of a believer in Jesus being "unequally yoked" with an unbeliever.
Paul asks: what cooperation can there be between virtue and wickedness? Those in Christ have "become the righteousness of God" (2 Corinthians 5:21). Those outside of Christ continue in their status as unrepentant, lawless sinners. The two cannot—must not—be joined together. To do so makes as little sense as trying to join light and darkness in fellowship. It can't be done. As soon as the light arrives, the darkness must vanish.
It's essential to realize Paul is not saying believers should never associate with unbelievers, at all (1 Corinthians 5:9–10). Believers should continue to live and function in the world, which includes contact with unbelievers (1 Corinthians 10:25–26). He has written to the Corinthians previously, though, not to sue each other in pagan courts of law (1 Corinthians 6:1–11), not to join themselves sexually to temple prostitutes (1 Corinthians 6:12–20), and not marry unbelievers (1 Corinthians 7:39).
Rather, Scripture's teaching here is that Christians must not enter into binding, partnering agreements with non-Christians.