18:15 Jesus declares, “If your brother sins against you, go and tell him his fault, between you and him alone.” Each element deserves comment. “If your brother sins” is literally “when your brother sins.” Brothers do sin against each other; Jesus here describes the way to address it. The Greek for “if” is ean, which commonly introduces general conditions: whenever brother sins against brother, go alone, explain the problem, and win the offending brother. Jesus does not envision a constant stream of confrontations. The topic is sin, not irritation, annoyance, breach of etiquette, or petty offense. Since the matter could eventually entail the summoning of witnesses and a hearing before the church, the instruction envisions believers acting in a local body.

The concern is sin “against you,” not any sin that anyone might commit. The following verses show that witnesses to the sin and eventually the church as a whole may be involved. Further, Galatians 6:1 indicates that church leaders may address any sin. “If anyone is caught in any transgression,” Paul says, the “spiritual” should “restore him in a spirit of gentleness.” James also says that “brothers” are responsible to bring back any sinner who “wanders from the truth” (James 5:19–20). Nonetheless, Jesus begins with the two people, the offender and the offended. Disciples must act when someone sins against them.

Most, but not all, early manuscripts have the words “against you” in Matthew 18:15. Textual critics note that the shorter text is ordinarily to be preferred, since copyists occasionally added clarifying notes, perhaps in a margin, that worked their way into the text. We can imagine that a copyist could add “against you” to “if your brother sins” to prevent a chaotic situation in which everyone believes they have freedom to confront any sin. But there are reasons to believe that “against you” belongs in the text. First, “against you” appears in most manuscripts in all textual families. Second, it is hard to see how the addition of a significant phrase could spread almost everywhere, but it is easy to see how “against you” could drop from some manuscripts. The Greek words for “against you” are very short and sound exactly like the ending of the longer Greek for word for “sins.” Since groups of copyists sometimes wrote as one person read, the similarity of sounds best explains the omission of these words from some manuscripts.

Consider the rationale for Jesus’ command. If someone sins against me, I should go, since I have direct knowledge of the event, as I understand it. Further, each disciple is responsible to seek peace or reconciliation. Paul writes, “If possible, so far as it depends on you, live peaceably with all” (Rom. 12:18). The offended have no right to sulk, gossip, withdraw, or recruit allies. Jesus says, “Go.”

The offended party reproves the sin. The Greek verb translated “tell . . . fault” (elenchō) belongs to the realm of investigation and inquiry or proof and conviction. The two overlap. Investigation comes first. If it reveals sin, reproof follows.

The conversation is private: “between you and him alone” (Matt. 18:1). This allows dialogue and repentance. A public rebuke is confrontational; it feels like a personal attack and leads to defensiveness and shame. If the goal is to “[gain] your brother,” then private conversation is best.

There is an exception. When a public person commits a public sin, public rebuke is fitting, since it can lead many astray. In Galatians 2, Peter (called Cephas) had been eating with Gentiles but then separated himself from them because he feared the “circumcision party”: Jewish Christians who still observed laws for circumcision, food, and separation from Gentiles. Since Peter knew that Gentiles were clean, or holy, by faith (Acts 10–11), this was a case of inconsistency and hypocrisy that threatened the gospel. His action implied that Gentiles had to do something—obey food laws—to be right with God. Because Peter’s conduct touched the gospel itself, Paul determined that he had to rebuke Peter “before them all” (Gal. 2:11–16).287

If we had nothing but Matthew 18:15, we might expect a flood of confrontations. But verse 16 implies that the matter is significant enough that witnesses could plausibly be called. Earlier, in 5:23–24, Jesus suggested that a matter must have enough weight to disrupt a worshiper as he or she offers a gift to God.

18:16–17 These verses address the problem of impenitence. When believers confront sin in each, the goal is to persuade the sinner to repent. Unfortunately, many are slow to repent. Pastorally, experience teaches that the greater the sin, the greater the likelihood that the brother who goes will be met with recalcitrance and blind self-righteousness.

If the first step fails, the offended party must “take one or two others . . . , that every charge may be established by the evidence of two or three witnesses” (v. 16). These witnesses saw the sin, in public cases. For a private offense, witnesses might testify that an attempt at reconciliation took place, to no avail. This process protects the innocent by thwarting groundless accusations. Jesus cites Deuteronomy 19:15—for Jesus and the apostles, the Mosaic requirement of two witnesses holds. This community-shaping element of the Mosaic law remains in force.

If the sinner, although claiming to be a brother, still fails to respond, the church takes up the matter.288 If he refuses to heed the church, “let him be to you as a Gentile and a tax collector” (Matt. 18:17). Of course, Jesus welcomes sinners and tax collectors—including Matthew himself—for evangelistic reasons (9:10–13; Luke 15). But here a professing believer refuses to repent after verifiable sin. Since Jesus has just said that humility, which leads to ready repentance, is a mark of kingdom life (Matt. 18:4; cf. Luke 18:14), the impenitent define themselves as outsiders. Therefore, if every step fails, the community of disciples “must publicly dissociate itself from a habitually sinning professed disciple.”289 Ideally, this path leads the sinner to see the gravity of the situation and reverse course. Excommunication is remedial, not punitive. (1 Cor. 5:1–11).

Excommunication also protects the flock of God, lest professing believers lead the naive astray (Rom. 16:17–18). Christians inevitably associate with sinners as they work and evangelize (1 Cor. 5:9–10). But disciples must not associate with so-called brothers who remain in sin (1 Cor. 5:11). If someone chooses acts that define himself as an outsider, the church should treat him accordingly. With excommunication there is yet hope of reconciliation through a fresh encounter with the gospel.

18:18–20 These verses reassure leaders who have cast out the impenitent. Jesus asseverates on his own authority, “Truly, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven” (v. 18). As at 16:19, a literal translation could read, “Whatever you bind on earth shall have been bound in heaven, and whatever you loose on earth shall have been loosed in heaven” (18:18).290 To bind is to prevent entry into the kingdom. To loose is to permit entry. Leaders bind when they warn the calloused sinner, “Unless you repent, we cannot regard you as an heir of life.” They loose when they say, “God welcomes repentant sinners” (11:20; cf. Luke 15:7, 10). When teachers say as much, they merely restate what God has declared. When pastors banish the impenitent from the church or grant membership to those who do repent (whatever their sin) they redeclare the gospel. The unrepentant have no place in the kingdom, especially if they persist despite warning. Believers face their sin and repent of it. Refusal to repent is a sign of unbelief.

Matthew does not mention elders or overseers, but later books demonstrate that elders or overseers must guarantee the integrity of the church. Paul charged the Ephesian elders to guard themselves and “all the flock, in which the Holy Spirit has made you overseers, to care for [or “shepherd”] the church of God, which he obtained [or “purchased”] with his own blood” (Acts 20:28). According to Acts 20:29–30, “wolves” will arise, teaching falsehood and seeking disciples for themselves. Elders protect the flock from doctrinal and moral deviation.

Because this task is thankless, Jesus gives leaders assurances. He promises that if two followers “agree on earth about anything they ask, it will be done for them by my Father in heaven” (Matt. 18:19). Populist Christianity tends to claim this as an abstracted and absolute promise. In extreme form, some think that their agreement—if bolstered by sufficient faith—can bind God to answer requests for health or prosperity. This foolishness both robs God of his sovereignty and violates the first principles of exegesis. It is clear, in context, that Jesus promises aid when, in the throes of church discipline, leaders agree on a path of action and ask the Father to sustain them in it. “Anything” translates pragma, which normally refers to a matter, task, affair—even a dispute. Therefore, Jesus promises the Father’s presence when two or three gather in his name to ensure that the church acts, as much as possible, like the bride of Christ. It stands by God’s grace, reclaims that grace by repentance, and honors that grace by striving for holiness.