Do not be deceived: “Bad company ruins good morals.” (1 Corinthians 15:33)

Paul warned that bad company corrupts good morals in the context of confronting those who denied the resurrection of the dead. This was an attack on the gospel itself, since the resurrection of Christ is central to the Christian message. Some within the church had embraced false ideas and began to corrupt the minds of others, leading them into heresy. Their influence was spiritually destructive, even fatal to salvation. It was not a trivial error. 

As he refuted the false doctrine, Paul also instructed the believers to separate themselves from such people. A message that denies the resurrection cannot save. To tolerate their presence or permit their voices to remain in the church was to expose the flock to poison. Remaining in their company meant submitting the mind to deception and training the heart to accept lies. Paul demanded separation and unwavering allegiance to the truth. The people of God must break fellowship with error, even if it severs relationships they once held dear.

This principle applies beyond the immediate context. The believer must refuse fellowship with those who persist in false doctrine or an ungodly lifestyle. He must separate from evil influences, including those who distort or oppose the gospel. This includes leaving churches and seminaries that tolerate heresy. To remain among them is to invite contamination. Their teachings are filth. Walk away without regret.