Paul said in 2 Cor. 6:14-15 Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? And what accord has Christ with Belial? Or what part has a believer with an unbeliever?
Now, Paul is getting into the root of the Corinthian’s real problem. They had apparently joined themselves with unbelievers and that was negatively affecting their relationship with Paul.
“do not be unequally yoked”: This is based on Deut. 22:9 which prohibited the yoking of two different animals. It, of course, speaks of joining two things that should not be joined. Clark says, “A very wise and very holy man was given his judgment on this point: ‘A man who is truly pious, marrying with an unconverted woman, will either draw back to perdition, or have a cross during life. The same may be said of a pious woman marrying an unconverted man. Such persons cannot say this petition of the Lord’s prayer, Lead us not into temptation. They plunge into it of their own accord.”’
However, Paul is speaking about much more than simply marriage. It applies really to anything that is not of God being allowed to influence our thinking. The issue at stake is influence. I.e. books, movies, television, magazines and relationships.
We all like to think that we can be around ungodly things and not be influenced. Paul reminded them in 1 Cor. 15:33, “Be not deceived: evil communications corrupt good manners.”
too indiscriminate about the things that they allow to influence their minds and lives. The Corinthians Christians were worldly in their thinking because of their associations.