1 Cor 5:9-13
9 I wrote to you in my letter not to associate with sexually immoral people— 10 not at all meaning the people of this world who are immoral, or the greedy and swindlers, or idolaters. In that case you would have to leave this world. 11 But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people. 12 What business is it of mine to judge those outside the church? Are you not to judge those inside? 13 God will judge those outside. “Expel the wicked person from among you.”
St Paul had given clear advice in the Scriptures on how to deal with professing believers who are immoral, greedy or are swindlers or idolaters and are unrepentant. He had also taken preventive action in warning Timothy and the Corinthian church of certain so-called brothers who were causing great harm to his ministry. 1 Tim 1:20; 2 Tim 4:14.
Ex-communication instructed by Paul was necessary to protect the Corinthian church when these sinful believers were unrepentant after exhausting confrontation of sin privately and before the church with evidence and witnesses, and sincere attempts to restore them. But ex-communication as a last resort is not an end in itself when Paul also instructed on possible future restoration and saving their souls.
The following sermon by Pastor Steven Cole gives an excellent overview of church discipline – the right steps to confront and to restore; and the necessity of ex-communication as a last resort in protecting the church.