Excommunication

The last but reversible step in church discipline, resulting in exclusion from the fellowship of believers. The grounds that Scripture suggests for excommunication include public sin and immorality.

Jesus Christ authorises the church to excommunicate a sinning brother

Matthew 18:15–18 The binding of sinners is thought to refer to their exclusion from God's people, and loosing, to their restoration after repentance (compare Matthew 16:19).

If your brother sins against you, go and confront him privately. If he listens to you, you have won your brother over. But if he will not listen, take one or two others along, so that ‘every matter may be established by the testimony of two or three witnesses.’ If he refuses to listen to them, tell it to the church. And if he refuses to listen even to the church, regard him as you would a pagan or a tax collector. Truly I tell you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.

Paul exhorts the Corinthian church to excommunicate an immoral brother

1 Corinthians 5:1–6 By “hand this man over to Satan” (see also 1 Timothy 1:20) Paul means to expel him, by putting him out into the devil's territory, in the hope that being officially ostracised, he might repent and forsake his wicked way. Such discipline was necessary not only for the reclaiming of the sinner but also for the safety and purity of the church (verse 6). See also 1 Corinthians 5:11–13

It is actually reported that there is sexual immorality among you, and of a kind that is intolerable even among pagans: A man has his father’s wife. And you are proud! Shouldn’t you rather have been stricken with grief and have removed from your fellowship the man who did this? Although I am absent from you in body, I am present with you in spirit, and I have already pronounced judgment on the one who did this, just as if I were present. When you are assembled in the name of our Lord Jesus and I am with you in spirit, along with the power of the Lord Jesus, hand this man over to Satan for the destruction of the flesh, so that his spirit may be saved on the Day of the Lord. Your boasting is not good. Do you not know that a little leaven works through the whole batch of dough?

Excommunicated offenders who repent are to be lovingly restored to fellowship

2 Corinthians 2:5–11 This passage probably refers to the offender mentioned in 1Corinthians chapter 5.