Excommunication is a religious censure used to deprive, suspend, or limit membership in a religious community or (as in the case of the Catholic Church) to restrict certain rights within it. Some groups use the term disfellowship instead. The word excommunication means putting [someone] out of communion. In some religions, excommunication includes spiritual condemnation of the member or group. Excommunication may involve banishment, shunning, and shaming, depending on the religion, the offense that caused excommunication, or the rules or norms of the religious community.
In Matthew 18:15-17 Jesus says that an offended Christian should first draw the offender's fault to the offender's attention privately; then, if the offender refuses to listen, to 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, to bring the matter before the church, and if the offender refuses to listen to the church, to treat the offender as "a Gentile and a tax collector".
In 1 Corinthians 5:1-8, a man is excommunicated by the church at Corinth for sexual immorality (incest). In 2 Corinthians 2:5-11, the man, having repented and suffered the punishment "inflicted of many," 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 [οἰκίαν, residence or abode, or "inmates of the house" (family)], neither bid him God speed: for he that biddeth him God speed is partaker of his evil deeds."
In Roman Catholic canon law, excommunication is a censure and thus a "medicinal penalty" intended to invite the person to change behavior or attitude, repent, and return to full communion. It is not an "expiatory penalty" designed to make satisfaction for the wrong done, much less a "vindictive penalty" designed solely to punish.