14Do not be mismatched with unbelievers. For what partnership is there between righteousness and lawlessness? Or what fellowship is there between light and darkness? 15What agreement does Christ have with Belial? Or what does a believer share with an unbeliever? 16What agreement has the temple of God with idols? For we are the temple of the living God; as God said, I will live in them and walk among them, and I will be their God, and they shall be my people. 17Therefore come out from them, and be separate from them, says the Lord, and touch nothing unclean; then I will welcome you, 18 and I will be your father, and you shall be my sons and daughters, says the Lord Almighty. (2nd Corinthians 6:14-18)
Do not be mismatched with the unbeliever (verse 14) is translated in the King James Bible as, “do not be unequally yoked with an unbeliever.” This consideration looks back to Deuteronomy 22:10. In that passage, God instructed Israel to not plow with an ox and a donkey yoked together. The compelling reason for this is that these two animals together could not plow a straight furrow. Their temperaments, natural instincts, and physical characteristics made it impossible. Paul’s analogy is plain, the Christian and the non-Christian cannot work together in serving God because they are drawn in different directions, no matter how well intended. Their spiritual temperaments and natural instincts are not compatible. The Christian is clean (pictured by the ox) while the non-believer (pictured by the donkey) is unclean (Deuteronomy 14:1-8) and are motivated by different principles.
Separation from the unsaved, however, does not mean an avoidance of them, for how then could the Christian be a faithful witness to them? But it does mean that the Christian is not to be in complicity with or in conformity to them. Let us, therefore, who are born again Christians strive to walk in a way that is God-honoring, separated from the world in our attitudes and deeds.
Transforming Power; The Work of God on Behalf of Man