The word excommunication means putting a specific individual or group out of communion. In some denominations, excommunication includes spiritual condemnation of the member or group. Excommunication may involve banishment, shunning, and shaming, depending on the group, the offense that caused excommunication, or the rules or norms of the religious community. The grave act is often revoked in response to sincere penance, which may be manifested through public recantation, sometimes through the Sacrament of Confession, piety or through mortification of the flesh.
In Matthew 18:15-17 Jesus says that an offended person should first draw the offender's fault to the offender's attention privately; then, if the offender refuses to listen, bring one or two others, that there may be more than a single witness to the charge; next, if the offender still refuses to listen, bring the matter before the church, and if the offender refuses to listen to the church, treat the offender as "a Gentile and a tax collector".
1 Corinthians 5:1-8 directs the church at Corinth to excommunicate a man for sexual immorality (incest). In 2 Corinthians 2:5-11, the man, having repented and suffered the "punishment by the majority" is restored to the church. Fornication is not the only ground for excommunication, according to the apostle: in 5:11, Paul says, "I am writing to you not to associate with anyone who bears the name of brother if he is guilty of sexual immorality or greed, or is an idolater, reviler, drunkard, or swindler - not even to eat with such a one."
In Romans 16:17, Paul writes to "mark those who cause divisions contrary to the doctrine which ye have learned and avoid them." Also, in 2 John 1:10-11, the writer advises believers that "whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son. If there come any unto you, and bring not this doctrine, receive him not into your house , neither bid him God speed: for he that biddeth him God speed is partaker of his evil deeds."