So far in Matthew 18 Jesus dealt with those who cause a little child to stumble (18:6-9) and the person who has wandered away from their faith (the one who has stumbled, 18:10-14). In this paragraph, Jesus addresses another related issue, a brother or sister in Christ who has some fault but has not yet stumbled and wandered away from the faith. As suggested by Craig Keener, this person may very well be a stumbling block to others, therefore they need to be addressed before they cause others to stumble (Matthew, 452).
Jesus is concerned his followers should discreetly confront those who are beginning to wander and bring them back into the flock as gently as possible. The earliest communities were very small house churches in the Jewish diaspora. As more gentiles were attracted to the Gospel, it is likely these house churches had to deal with serious conflicts between disciples of Jesus.
There are several difficult issues in 18:15-20. Jesus appears to lay down a process for church discipline, and Matthew’s use of church seems anachronistic. There was no church prior to the resurrection, although it is possible the word can refer to the community of Jesus followers, something like the yahad at Qumran. If this is the case, is there a direct application of the process to modern Christians as they confront one another over their faults?
Davies and Allison (Matthew 2:783) point out first that this is a serious and intentional sin, rather than a one-time insult, something which can be overlooked as a mistake or misunderstanding Second, this is a sin committed against a brother or sister in Christ. This does not apply to people outside of the church since they are not part of the family. Third, this is a private sin, rather than a public offense. If it were known by the community, then it should be dealt with by the whole community.
The disciple of Jesus should attempt to deal with personal offenses privately. The verb is the typical one expected for sin (ἁμαρτάνω, aorist subjunctive). There is nothing here which implies this is offending someone’s preferences. For example, this is not about confronting someone for wearing a bolo tie and cowboy boots to church, nor is this about coming to church with a face full of piercings and tattoos. These things are matters of (good or bad) taste and not personal sin which is damaging to one’s spiritual life.
The phrase “point out their fault” (ESV) is a single word, ἐλέγχω. This verb can have the connotation of “to scrutinize or examine carefully, bring to light, expose” (BDAG) as in Ephesians 5:13. But it is sometimes used for “express strong disapproval of someone’s action” (BDAG), to reprove or to correct someone (as in 2 Tim 4:2, “reprove, rebuke, and exhort, with complete patience and teaching”).
Jesus describes an escalation from a private confrontation to a semi-private meeting, and finally to a public meeting with the church. Two or three witnesses are likely drawn from the Law (citing Deut 19:15, cf., Num 35:30). No court matter could be established by a single witness, at least one or two other witnesses were required. Paul also used this principle of two or three witnesses in 2 Corinthians 13:1 (although Paul himself was the second and third witness) and 1 Timothy 5:19 (dealing with the sin of an elder). The Second Temple document Testament of Gad also recommends a private meeting, “speaking to him in peace.”
Testament of Gad 6 Now, my children, each of you love his brother. Drive hatred out of your hearts. Love one another in deed and word and inward thoughts. 2 For when I stood before my father I would speak peaceably about Joseph, but when I went out, the spirit of hatred darkened my mind and aroused my soul to kill him. 3 Love one another from the heart, therefore, and if anyone sins against you, speak to him in peace. Expel the venom of hatred, and do not harbor deceit in your heart. If anyone confesses and repents, forgive him. 4 If anyone denies his guilt, do not be contentious with him, otherwise he may start cursing, and you would be sinning doubly. 5 In a dispute do not let an outsider hear your secrets, since out of hatred for you he may become your enemy, and commit a great sin against you. He may talk to you frequently but treacherously, or be much concerned with you, but for an evil end, having absorbed from you the venom. 6 Even if he denies it and acts disgracefully out of a sense of guilt, be quiet and do not become upset. For he who denies will repent, and avoid offending you again; indeed he will honor you, will respect you and be at peace. 7But even if he is devoid of shame and persists in his wickedness, forgive him from the heart and leave vengeance to God.
The final step is a public confrontation with the whole congregation. In the context of the earliest followers of Jesus, this would not be a large assembly. Gatherings were small groups of believers worshiping in homes or other semi-private places. This is not a public tribunal before a crowd of hundreds. If after the first confrontation the person does not listen (μὴ ἀκούσῃ) the semi-private meeting is necessary. But if he refuses to listen (παρακούσῃ, to ignore something which has in fact been heard, BDAG) to the two or three witnesses, a public meeting is necessary. Anyone who refuses to hear a word of correction from two or three fellow disciples implies the person caught in a sin disagrees they are in sin. They do not believe their behavior (or belief) is a fault which must be corrected. Looking ahead on what “binding and loosing” means in the next saying, the person may disagree with the community decision to consider something behavior (or belief) to be sinful (or not).
If a person does not recognize their sin, the final step is to treat the offending person as a Gentile or a tax-collector. This appears harsh since the Jewish people avoided contact with Gentiles (or those who worked for them, like a tax-collector). When the disciples visited the villages of Galilee, those which rejected the disciples were treated like Gentiles (shake of the dust of their cloaks). When Paul is rejected in a synagogue, he often does the same thing to indicate he will treat those who have rejected his teaching like a Gentile.
The problem is how this works out in real life. Some people really do enjoy pointing out another person’s fault. The Internet is full of people who have nothing better to do than argue about theological issues and condemn someone’s practice of their Christian faith. Some of those issues may be legitimate, but most of the time there is condemnation without any real engagement.
In the Sermon on the Mount Jesus talked about how one confronts a fellow disciple because of a sin. The disciple ought to deal with their own sin, the “log in your own eye,” before confronting someone over a minor sin, the “speck in their eye.” If the disciple of Jesus is busy dealing with their own spiritual life, then they will “see clearly” (Τότε διαβλέψεις). In Matthew 7:3-5, Jesus says the one who has dealt with a particular problem is able to gently correct a fellow disciple. To “gently correct” is the guiding principle in Matthew 18:15 as well.