11 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. 12 It isn't my responsibility to judge outsiders, but it certainly is your responsibility to judge those inside the church who are sinning. 13 God will judge those on the outside; but as the Scriptures say, "You must remove the evil person from among you."
Matthew Henry's Commentary on 1 Corinthians 5:11-13
Commentary on 1 Corinthians 5:9-13
(Read 1 Corinthians 5:9-13)
Christians are to avoid familiar converse with all who disgrace the Christian name. Such are only fit companions for their brethren in sin, and to such company they should be left, whenever it is possible to do so. Alas, that there are many called Christians, whose conversation is more dangerous than that of heathens!