1 Cor 5:9-11 says, When I wrote to you before, I told you not to associate with people who indulge in sexual sin. But I wasn’t talking about unbelievers who indulge in sexual sin, or are greedy, or cheat people, or worship idols. You would have to leave this world to avoid people like that. I meant that you are not to associate with anyone who claims to be a believer yet indulges in sexual sin, or is greedy, or worships idols, or is abusive, or is a drunkard, or cheats people. Don’t even eat with such people.
Holy Bible, New Living Translation
We have often been told to not associate with unbelievers, thinking that they are the ones in the world. However, in this scripture we see that a true unbeliever is someone who claims to be a Christian with his mouth but does not walk in God’s ways. A true believer is one that carries not only the word of God in his mouth, but also has the nature of the word ruling his life. Christ is man’s true nature. Time to walk!