The apostle Paul’s instructions to the Corinthian church fully showed this truth. He began by telling the Christians there not be divided, but united in the mind of Christ, saying “…Agree, and [let] there be no divisions among you, but [be of] the same mind and in the same judgment” (1:10).
Christians agreement and faithfulness can only be maintained when we aren’t deceived into thinking that sin, or the influence of sinful people, doesn’t affect us. So Paul warned, “Do not be deceived…the unrighteous will not inherit the kingdom of God,” and he listed a number of sexual sins and other destructive behaviors that these Christians used to do, but they’d been cleansed of in Christ (1 Cor. 6:9-11). It was imperative that they no longer do these things. They also needed to know that hanging around the people who still did them was destructive as well. So he said, “Do not be deceived: ‘Bad company corrupts good morals’” (1 Cor. 15:33).
The apostle was obviously worried some Christians were too close to worldly-mind and poor behaving people. So he reminded them “You were bought with a price; do not become slaves of men” (1 Cor. 7:23) and “Do not be bound together —unequally yoked - KJV— for what partnership have righteousness and lawlessness?” (2 Cor. 6:14).
How could Christians get so wrapped up in so many sinful things and become entangled with such sinful people? Selfishness and ignorance are usually culprits, so he instructed them about priorities and maturity, saying, “Let no one seek his own good, but that of his neighbor” (1 Cor. 10:24), and “Brethren, do not be children in your thinking; [but] mature” (1 Cor. 14:20)