Many Christians rightly look for a church that preaches the word. This is a fundamental “must” of a biblical and apostolic church: to preach the word – the full counsel of God, both law and gospel – in and out of season (Matt. 28:19-20, 1 Cor. 9:16, 2 Tim. 4:2, etc.). And, of course, Christian churches must also administer the two sacraments Christ has lovingly given us (Matt. 28:19, 1 Cor. 11:20, etc.). These two things are non-negotiable; if a church does not do them, it isn’t a church at all. So the Reformers called preaching the word and administering the sacraments two marks of a true Christian church (BCF 29).
But there’s a third mark that many Christians don’t think about as much when they look for a church: Christian discipline. Yet Jesus very clearly told his church in Matthew 18 that we are to use the keys of the kingdom. That is, we are to proclaim forgiveness to all who truly repent and proclaim judgment to all who will not repent (cf. 1 Cor. 5:1-13).
Why should Christian churches discipline those unrepentant among them who live an unbiblical life or believe an unbiblical doctrine? Simply put, because Jesus and Paul told us to. But there are other biblical and practical reasons for Christian discipline. The Westminster Confession of Faith says it well (I’ve edited it slightly for ease of reading):
“Church censures [rebukes/reprimands] are necessary 1) for the reclaiming and gaining of offending brethren, 2) for deterring of others from like offenses, 3) for purging out that leaven which might infect the whole lump, 4) for vindicating the honor of Christ, 4) for the holy profession of the gospel, and 5) for preventing the wrath of God, which might justly fall on the church if they allow his covenant to be profaned by obstinate sinners. (cf. 1 Cor. 5:1-13, 1 Tim. 5:20, Matt. 7:6, 1 Tim. 1:20, 1 Cor. 11:27-34, Jude 23).” WCF 30.3
When someone in a church is unrepentant, how should the elders deal with him or her? With love, firmness, patience, and prayer. But also, more specifically, like this: “the officers of the church are to proceed by admonition; suspension from the sacrament of the Lord’s Supper for a season; and by excommunication from the church, according to the nature of the crime and demerit of the person (1 Thess. 5:12, 2 Thess. 3:6, 14-15, 1 Cor. 5:4-5, 13).” WCF 30.4
What is excommunication? Excommunication “is a solemn declaration by an ecclesiastical judicatory (church court) that the offender is no longer considered a member of the body of Christ” (BCO VI.B.5). Excommunication is one of the hardest parts of church life; it is something done with many prayers, tears, and even trepidation. It might offend some. It might cause others to leave the church. Many elders will lose much sleep over this. Excommunication has to do with the eternal destiny of a person’s soul. It is no light matter.
But it has to be done in the cases of a continual and unrepentant hard heart. It is for the good of Christ’s church and the honor of his holy name. We must prayerfully keep these things front and center when we administer Christian discipline. Whether people like it or not, Christian discipline is indeed one of the three marks of a true Christian church.