1 Corinthians 15:33 Do not be deceived: “Bad company ruins good morals.”
Proverbs 9:6 Leave your simple ways, and live, and walk in the way of insight.”
Galatians 6:7 Do not be deceived: God is not mocked, for whatever one sows, that will he also reap.
2 Timothy 2:16-17 But avoid irreverent babble, for it will lead people into more and more ungodliness, and their talk will spread like gangrene.
Hebrews 12:15 See to it that no one fails to obtain the grace of God; that no “root of bitterness” springs up and causes trouble, and by it many become defiled;
Paul deals with the moral problems of the Corinthians: envy, divisions, pride, immorality, greed, irreverence, and selfishness. How much of this came in because of they kept evil company? This speaks to the vital need described in Romans 12:2: do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God. By keeping evil company, the Corinthian Christians were being conformed to this world, and they needed to be transformed by the renewing of your mind. Christians must let the Word of God shape their thinking, not the evil company of this world.
It is very easy to “get conformed to the world”. The world does not recognize God. The world does not speak about God, other than to say He does not exist. The world tries to replace the joy, hope, and trust in Jesus Christ alone with everything that promises to satisfy the soul but leaves the soul lacking and wanting more, something better. All-day long the world denies, rejects, and proclaims its self-center self-reliance and calls things of God foolish and false. Paul is saying rid yourselves of these influences. Take your guidance from the Word of God.