10 But I had not in mind the sinners who are outside the church, or those who have a desire for and take the property of others, or those who give worship to images; for it is not possible to keep away from such people without going out of the world completely: 11 But the sense of my letter was that if a brother had the name of being one who went after the desires of the flesh, or had the desire for other people's property, or was in the way of using violent language, or being the worse for drink, or took by force what was not his, you might not keep company with such a one, or take food with him. 12 For it is no business of mine to be judging those who are outside; but it is yours to be judging those who are among you;
Matthew Henry's Commentary on 1 Corinthians 5:10-12
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!