Paul firmly stipulated that both husband and wife had to be "equally yoked" with Jesus Christ and each other for marriage to last. They must not be "unequally yoked." The King James version of the Bible speaks of being "unequally yoked," while the Revised Standard Version uses the term, "mismated."
Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? And what communion hath light with darkness? (2 Corinthians 6:14 KJV)
Do not be mismated with unbelievers. For what partnership have righteousness and iniquity? Or what fellowship has light with darkness? What accord has Christ with Belial? Or what has a believer in common with an unbeliever? (2 Corinthians 6:14,15 RSV)
The genuine presence of Jesus Christ through his Holy Spirit as a Third Person in the marriage is the only guarantee that a marriage will continue to grow in love and happiness. He is the only Person who should ever be allowed to come between a husband and wife.
With His presence in the relationship, that delicious initial attraction between the spouses will never lose its spark. He will be constantly at work, drawing them together and renewing their love daily through the power of the Holy Spirit.
c. Gordon Williams Evangelistic Association 2008.