Bible Commentaries
Matthew 18

Dr. Constable's Expository NotesConstable's Expository Notes

Introduction

4. Instructions about the King’s personal representatives ch. 18

Chapter 18 contains the fourth major discourse that Matthew recorded (cf. chs. 5-7; ch. 10; Matthew 13:1-53; chs. 24-25), His Discipleship Discourse. This discourse continues Jesus’ instruction of His disciples that He began in Matthew 17:14. Instead of focusing on Jesus, the Lord’s teaching focused on the disciples and their responsibilities as His representatives. The theme of this discourse is humility. The theme of the Sermon on the Mount was righteousness. The theme of the Mission Discourse in chapter 10 was ministry. The theme of the Kingdom Discourse in chapter 13 was the kingdom, and the theme of the Olivet Discourse would be the Second Coming.

Kingsbury called the theme of this speech "life within the community of the church" and outlined it as follows: (I) On True Greatness as Consisting in Humbling Oneself so as to Serve the Neighbor (Matthew 18:1-14); and (II) On Gaining and Forgiving the Errant Disciple (Matthew 18:15-35). [Note: Kingsbury, Matthew as . . ., p. 112.]

Apart from the second question (Matthew 18:18), this discourse proceeds as a unit of teaching similar to the first discourse (chs. 5-7) and the second discourse (ch. 10), but not the third discourse (ch. 13).

"The theme of this discourse is not so much individual discipleship (though several of the examples and instructions are expressed in the singular) as the corporate life of those who are joined by their common commitment as disciples, with special attention being given to the strains and tensions to which such a life is exposed through self-concern and lack of care for fellow disciples, through bad examples and errant behavior, and through an unwillingness to forgive as we have been forgiven." [Note: France, The Gospel . . ., p. 672.]

Verses 1-2

The writer introduced and concluded this discourse, as he did the others, with statements suggesting that Jesus delivered this address on one specific occasion (cf. Matthew 5:1; Matthew 7:28-29). The last two discourses in Matthew were responses to questions from the disciples (Matthew 18:1; cf. Matthew 24:1-3).

"At that time" probably means "in that stage of Jesus’ ministry" (cf. Matthew 10:19; Matthew 26:45). The preceding revelations about the King and the kingdom led the disciples, probably the Twelve, to express interest in who would be greatest in the kingdom (cf. Mark 9:33-38; Luke 9:46-48). Perhaps Peter’s leadership among the disciples and Peter, James, and John’s privilege of seeing Jesus transfigured made this one of their growing concerns. Jesus had taught that there would be distinctions in the kingdom (Matthew 5:19; Matthew 10:32-33). If Jesus gave this teaching in Peter’s house, the child may have been his (cf. Matthew 17:25; Mark 9:33), but this is only a possibility.

In any case what Jesus did in setting a child forward as an example for adults to follow was shocking in His day. People of the ancient Near East regarded children as inferior to adults. They did not receive the consideration that adults enjoyed until they reached adult status. Children were to look to adults as examples to follow. Now Jesus turned the tables and urged His disciples to follow the example of a child. To do so would require humility indeed.

Verses 1-4

The introduction of the theme of humility 18:1-4 (cf. Mark 9:33-36; Luke 9:46-47)

Verses 3-4

Jesus announced His revolutionary words with a solemn introductory formula (cf. Matthew 5:18). He said it was necessary that His disciples change and became as little children. The word "converted" in the NASB is misleading. Jesus was not speaking about "getting saved." Childlikeness was necessary for entrance into the messianic kingdom. Children have many characteristics that distinguish them from adults, but because of the disciples’ concern with position in the kingdom and the teaching that follows, humility is clearly in view. Young children have little concern about their personal prestige and position in relation to other people.

In one sense the disciples had already humbled themselves as children when they believed on Jesus. This gave them access to the kingdom. However in another sense they had abandoned that attitude when they became concerned about their status in the kingdom. They needed to return to their former childlike attitude. Similarly they had exercised great power through simple faith in Jesus, but as time passed they got away from depending on Him, lost their power, and needed to return to dependent faith. Likewise Peter had made a great confession of faith in Jesus, but shortly after that he regressed and failed to submit to Jesus.

Matthew 18:3 also clarifies that the kingdom was still future when Jesus said these words. [Note: Cf. Montefiore, The Synoptic . . ., 2:247.] The disciple who humbled himself as a little child would be the greatest in the kingdom. Greatness in the kingdom was what these disciples wanted (Matthew 18:1). Jesus had previously commended childlike characteristics to His disciples (Matthew 5:3; Matthew 11:25).

Since Jesus was speaking to disciples who believed on Him (Matthew 16:16), it appears that He used the polar expressions "not enter the kingdom" and "greatest in the kingdom" to clarify His point. His point was the importance of humility. Jesus had previously said that if the disciple’s eye caused him to stumble he should gouge it out (Matthew 18:9; cf. Matthew 5:29). That was a similar extreme statement (hyperbole) made to clarify a point.

Verses 5-6

The child in view in these verses is not a literal child but the disciple who has humbled himself or herself and in so doing has become childlike (Matthew 18:3-4). Jesus was speaking of receiving a humble disciple of His in Matthew 18:5. (Jesus taught the importance of receiving a little child in Mark 9:36-37 and Luke 9:48.) Whoever does this "in Jesus’ name" welcomes the disciple because he or she is one of Jesus’ disciples, not because that one is personally superior, influential, or prominent. The person who welcomes one of Jesus’ humble disciples simply for Jesus’ sake virtually welcomes Jesus Himself (cf. Matthew 10:42). In this context, as well as in chapter 10, Jesus was speaking of welcoming in the sense of extending hospitality with its attendant encouragement and support. "To receive" (Gr. dekomai) means to receive into fellowship. [Note: Thayer, s.v. "dekomai," p. 130.]

The antithesis in Matthew 18:6 involves not welcoming a disciple but rejecting or ignoring him. Withholding supportive encouragement would cause a disciple to stumble in the sense that it would make it harder for him to do his work. Jesus was not speaking of causing the disciple to stumble by leading him or her into apostasy. The contrast makes this clear. Discouraging the disciple amounts to rejecting the Master. Consequently drowning at sea would be better for the offender than having to face Jesus’ condemnation in hell for rejecting Him (Matthew 18:8-9). Again, hyperbole presents the consequences as extremely bad. "Little ones who believe in me" (Matthew 18:6) defines the disciples in view. This is the only place in the Synoptics where "believe in me" occurs. This phrase is very common in John’s writings.

Drowning was a Greek and Roman method of execution but not a Jewish one. [Note: Carson, "Matthew," p. 398.] The type of millstone in view was a large one that a donkey would rotate, not the small hand millstone that every Palestinian woman used to prepare her flour. [Note: Edersheim, The Life . . ., 2:120.] Drowning in this way would be horrible, but it would be better than perishing in the lake of fire (Matthew 18:8).

Verses 5-14

The seriousness of impeding the progress of a disciple 18:5-14 (cf. Mark 9:37-50; Luke 9:48-50)

The major sub-theme of this discourse is offenses (Gr. skandalon, stumbling blocks). The humble disciple will be careful not to put a stumbling block in the path of another disciple as that one proceeds toward the kingdom.

Verse 7

Jesus pronounced woe on the world because it is the source of opposition to Him and His disciples, the source of all stumbling. The NIV translation may be a little misleading here. "Woe" announces judgment (cf. Matthew 11:21; Matthew 23:13-32). It is inevitable that the world will reject Jesus’ disciples, but God will hold those who do reject them responsible (cf. Isaiah 10:5-12; Acts 4:27-28).

Verses 8-9

Jesus next warned His disciples about the possibility of their doing what the world does, namely, making it difficult for another disciple to fulfill his or her mission for Jesus. In the context, one’s competitive pride of position might cause another disciple to stumble (Matthew 18:1). The illustrations Jesus used recall Matthew 5:29-30, where He also urged His disciples to discipline their thoughts and motives.

The point of this section was the seriousness of rejecting or opposing Jesus’ disciples in their work of carrying out His will. It is as serious as child abuse.

Verses 10-11

Jesus warned His disciples not to look down on His followers who were very humbly following Him. The Twelve were in danger of using worldly standards to measure and give value to their fellow disciples, as we are today (cf. Matthew 5:3). Judas Iscariot was one disciple who failed to heed this warning.

Many interpreters believe that the last part of Matthew 18:10 teaches that God has guardian angels who take special care of small children. However the context of Matthew 18:10 is not talking about small children but disciples who need to be as humble as small children. Furthermore the angels in this passage are continually beholding God’s face in heaven, not watching the movements of small children on earth. Evidently the angels in view are the supernatural messengers (the normal meaning of "angels") who assist God’s people (Hebrews 1:14). This seems to me to be more likely than that they are the spirits of believers after death who constantly behold God’s face (cf. Acts 12:15). [Note: B. B. Warfield, Selected Shorter Writings, 1:253-66.] Another view is that they are the spirits of children who have died. [Note: Thomas, p. 268.] Are there guardian angels for children? I like to think there are because of God’s concern for children (e.g., Matthew 19:14-15), but I cannot point to a verse that teaches this explicitly.

The Jews believed that only the most knowledgeable of the angels beheld God’s face while the rest remained outside awaiting His bidding. [Note: Edersheim, The Life . . ., 2:122.] Jesus taught that the angels responsible for believers all have access to Him, because of God’s love for His own.

Matthew 18:11 does not appear in the earliest ancient copies of Matthew’s Gospel. Probably scribes influenced by Luke 19:10 included it here in later versions of the text.

Verses 12-13

Having taught the importance of humility, Jesus now illustrated it with a parable. Jesus taught the same parable on a different occasion to teach a slightly different lesson (Luke 15:4-7). His purpose there was evangelistic whereas His purpose here is pastoral.

The shepherd in the story is God (Matthew 18:14). The sheep are those who follow Him, namely, Jesus’ disciples (cf. Matthew 10:6; Matthew 15:24). God has concern for every one of His sheep and seeks to restore those of them that wander away from Him. He has such great concern for the wayward that when they return to Him He rejoices more than over those who did not wander away. This does not mean that God loves His wayward sheep more than He loves His faithful sheep. It means that when wayward sheep return to Him it gives Him special joy.

Since God has such great concern for His disciples who go astray, His disciples should be very careful not to do anything that would cause one of His sheep to go astray. [Note: Plummer, p. 252.]

Notice again Jesus’ identification of Himself and God in this parable. Jesus’ disciples are God’s sheep. Therefore Jesus and God are one.

Verse 14

This verse concludes the argument of the discourse thus far. The heavenly Father does not want one of Jesus’ humble disciples to wander away from his calling in life as a disciple because someone has discouraged, rejected, or opposed him. Moreover He does not want His disciples, of all people, to be responsible for this. Perishing in this context does not mean loss of salvation but the ultimate result of failing to achieve God’s goal for him or her as a disciple, namely, a wasted life.

Verse 15

By using the term "brother" Jesus encouraged a humble approach. The disciples should deal with each other as brothers rather than as superiors and inferiors (cf. 1 Timothy 5:1-2). Contextually the sin in view is probably despising a brother or sister. However, Jesus did not specify what it was, but He implied that it was any sin that takes the disciple away from the Shepherd. Jesus commanded His disciples to go to such a person and reprove him in private. The disciple must take the initiative and confront (cf. Galatians 6:1).

". . . if it is hard to accept a rebuke, even a private one, it is harder still to administer one in loving humility." [Note: Carson, "Matthew," p. 402.]

"The possession of humility is proven not by passively waiting for one to beg forgiveness and then granting it. Rather, it is manifested by actively seeking out the erring brother and attempting to make him penitent." [Note: Toussaint, Behold the . . ., p. 217.]

The verb "reprove" or "show him his fault" (Gr. elencho) means "to convict" in the sense of producing an awareness of guilt, not in the sense of lording it over someone (cf. 1 Corinthians 9:19-22; 1 Peter 3:1). The objective should be the erring brother or sister’s restoration, not the initiator’s glorification (cf. Luke 17:3-4; 2 Thessalonians 3:14-15; James 5:19-20). This approach was one that the Mosaic Law had taught too (Leviticus 19:17), and that the Rabbis also supported. [Note: Edersheim, The Life . . ., 2:123.] .

"Sin, of whatever form, is not to be tolerated within the disciple community, but is to be dealt with when it is noticed. But this is to be done with sensitivity and with a minimum of publicity." [Note: France, The Gospel . . ., p. 692.]

Verses 15-20

The restoration of a wayward disciple 18:15-20

Jesus proceeded to explain what a humble disciple should do when a brother or sister disciple has wandered from the Shepherd and the sheep.

Verse 16

The Mosaic Law had also advocated the second step that Jesus taught (Deuteronomy 19:15). However, Jesus broadened the field of civil law that the Deuteronomy passage covered to include any sin about which a disciple might need rebuke. Jesus was not perpetuating the whole Mosaic Law. He was simply carrying over these provisions in the Law that He declared were now binding on His disciples.

Probably the function of the witnesses is to witness to the erring disciple’s reaction to the confrontation. This seems to have been the purpose in the Deuteronomy passage. Their presence would be an added inducement to return to the fold of the faithful. These seem to be witnesses to the confrontation, not to the sin. If the brother or sister proved unrepentant and the initiator needed to take the third step (Matthew 18:17), witnesses to the confrontation might be necessary.

Verse 17

The third step, if necessary, is to report the situation to the "church." This is the second reference to ekklesia in Matthew and the only other occurrence of this word in the four Gospels. As I pointed out above (cf. Matthew 16:18), this word means "a called out assembly of people." Jesus probably used it in a wide sense here. We have noted that the terms "lord," "disciple," "apostle," and others came to have more specific meanings as God’s kingdom plan unfolded. Jesus predicted the existence of the church, the body of Christ, in Matthew 16:18. However the disciples undoubtedly understood Him to mean simply His band of disciples. Jesus was talking about the assembly of His disciples that He was calling out of the world to represent Him that He knew would become a large body. He knew this would be the church as we know it, but the disciples must have thought He meant just themselves in a collective sense. Perhaps they thought He was referring to a Jewish assembly, a synagogue. [Note: Walvoord, Matthew: . . ., p. 137.]

Jesus revealed almost nothing about the church in the Gospels, as the absence of references to it in these books indicates. The disciples were struggling to grasp Jesus’ deity, His suffering servant role, and His passion. Jesus did not confuse them with much revelation about the form that their corporate identity would take following His ascension. He did not even do that after His resurrection (Acts 1:6-8). That revelation came through His apostles after His ascension. We have it in Acts and the Epistles.

When Jesus said, "Tell it to the church (assembly)," the disciples probably heard, "Tell it to all the other disciples, not just the two or three witnesses." Applying this command today becomes more difficult because the number of the disciples is incalculable and they live around the globe. In most situations the scope of public announcement would be a local church congregation, the particular collection of disciples of which the wayward brother is a part.

If the erring disciple does not respond to the church’s encouragement to return to the Shepherd, Jesus said the disciples should treat such a person as a Gentile and a tax gatherer. This does not mean the disciples should receive him or her warmly as Jesus received such people (Matthew 8:1-11; Matthew 9:9-13; Matthew 15:21-28). The context, as well as the New Testament parallels to this exhortation, shows that Jesus had exclusion in mind (cf. Romans 16:17; 2 Thessalonians 3:14). Jesus probably used Gentiles and tax gatherers as examples because the Jews typically withdrew from them. That is what He wanted His disciples to do regarding the erring brother or sister. The "you" in the Greek text is singular indicating that the initiator is a single individual and the sphere of life Jesus had in mind throughout this section was interpersonal relations (cf. Matthew 18:15)

"He cannot be treated as a spiritual brother, for he has forfeited that position. He can only be treated as one outside the church, not hated, but not held in close fellowship." [Note: Wiersbe, 1:66.]

Neither Jesus nor the apostles specified the exact form this discipline should take (e.g., excommunication, exclusion from the Lord’s Supper, social isolation, withheld table fellowship, etc.). France argued that since the sphere of life in view is interpersonal relationships, the guilty party should only suffer isolation from the initiator of action, not the whole community of believers. [Note: France, The Gospel . . ., pp. 690-94.] However, it seems that if the whole church gets involved in reproving the offender, some sort of communal, as well as individual, punishment would be involved. Consequently I assume that Jesus intended the disciples involved in such situations to make these determinations on the basis of all the facts in each particular case. However, it seems to be going too far to put the offender in a situation in which it would become impossible for him or her to repent and experience restoration later. The objective of all discipline is ultimately restoration, not exclusion. [Note: See J. Carl Laney, "The Biblical Practice of Church Discipline," Bibliotheca Sacra 143:572 (October-December 1986):353-64; and Ted G. Kitchens, "Perimeters of Corrective Church Discipline," Bibliotheca Sacra 148:590 (April-June 1991):201-13.]

Verse 18

This verse is identical to Matthew 16:19. There Jesus was talking specifically about the messianic kingdom. Here He was speaking more generally about how His disciples should conduct themselves in humility. The "whatever" again seems to include people and privileges in view of how the Old Testament describes the stewards’ use of keys. The disciples would determine God’s will in a particular instance of rendering judgment in the church. Hopefully they would consult the Scriptures and pray to do this. Then they would announce their decision. With their announcement they would give or withhold whatever the judgment might involve, but they would really be announcing what God, the divine authority, had already decided. Their decision would be God’s will for the person being disciplined, assuming they had obtained the will of God before announcing it. [Note: See Craig S. Keener, "Exegetical Insight," in William D. Mounce, Basics of Biblical Greek: Grammar, p. 115.]

"To Peter the King promised authority in the kingdom, assuring him of guidance in the use of that authority. Now the Lord instructs His disciples concerning the subject of discipline in the church and also promises divine direction in their decisions." [Note: Toussaint, Behold the . . ., p. 218.]

Verses 19-20

It should be obvious from the context that this promise does not refer to whatever two or three disciples agree to ask God for in prayer. The Bible contains many promises concerning prayer (cf. Matthew 7:7-8; Matthew 21:22; John 14:13-14; John 15:7-8; John 15:16; 1 John 5:14-15; et al.), but this is not one of them.

In the context "anything" refers to any judicial decision involving an erring disciple that the other disciples may make corporately. God has always stood behind His judicial representatives on earth when they carry out His will (cf. Psalms 82:1). This is a wonderful promise. God will back up with His power and authority any decision involving the corporate discipline of an erring brother or sister that His disciples may make after determining His will. [Note: See C. Samuel Storms, Reaching God’s Ear, pp. 254-58.]

Here again (Matthew 18:20) Jesus takes God’s place as "God with us" (Matthew 1:23; Matthew 2:6; Matthew 3:3; Matthew 11:4-8; cf. Matthew 28:20). This statement implies a future time when Jesus would not be physically present with His disciples, the inter-advent age, specifically the period following His ascension and preceding His return. Jesus anticipated His ascension.

One writer argued that Matthew 18:18-20 are the center of a structural and theological chiasm that embraces Matthew 17:22 to Matthew 20:19. [Note: David McClister, "’Where Two or Three Are Gathered Together’: Literary Structure as a Key to Meaning in Mat_17:22 to Mat_20:19," Journal of the Evangelical Theological Society 39:4 (December 1996):549-58.] This thesis seems a bit stretched to me.

Verses 21-22

Jesus had been talking about excluding rather than forgiving (Matthew 18:17). This led Peter to ask how often he as a disciple should forgive an erring brother before he stopped forgiving. The rabbis taught that a Jew should forgive a repeated sin three times, but after that there need be no more forgiveness (Amos 1:3; Amos 2:6). [Note: Carson, "Matthew," p. 405; Lenski, p. 708.] Peter suggested seven times and probably felt very magnanimous doing so. Seven was a round number, sometimes regarded as a perfect number, obviously exceeding what the scribes taught (cf. Leviticus 26:21; Deuteronomy 28:25; Psalms 79:12; Proverbs 24:16; Luke 17:4).

Jesus’ response alluded to Genesis 4:24 where the ungodly Lamech said, "If Cain is avenged sevenfold, then Lamech seventy-sevenfold." Lamech claimed to have taken even more revenge on the man who struck him than God had taken on Cain for killing his brother Abel. Jesus turned Lamech’s bad example around and urged his disciples to practice generous forgiveness when their brothers hurt them.

The NASB has Jesus saying "seventy times seven" whereas the NIV translators wrote "seventy-seven times." Probably the NIV is correct since Jesus quoted the Septuagint of Genesis 4:24 exactly here, and it has "seventy-seven times." Even though the difference between these two translations is great numerically, it is not a very important difference. Jesus was not specifying a maximum number of times His disciples should forgive their brothers. Neither was He wiping out what He had just taught about confronting an erring brother (Matthew 18:15-20). His point was that disciples who are humble should not limit the number of times they forgive one another nor the frequency with which they forgive each other. The following parable of the unmerciful servant clarified this point.

Verses 21-35

The importance of forgiving a disciple 18:21-35

From a discussion of discipline Jesus proceeded to stress the importance of forgiveness. Sometimes zealous disciples spend too much time studying church discipline and too little time studying the importance of forgiveness.

Verse 23

Since Jesus required His disciples to forgive this way, the kingdom had become similar to what He proceeded to describe, not the king in the parable but the whole parable scene. The whole parable taught a certain type of interpersonal relationship based on forgiveness. This parable illustrates kingdom conditions, conditions that will prevail when Jesus establishes His kingdom. Jesus was not saying the kingdom was in existence then any more than He was saying that the conditions He described were already in existence. He argued that kingdom conditions should be those that the King’s disciples should seek to follow in their lives now since they already live under the King’s authority (cf. chs. 5-7; esp. Matthew 6:12; Matthew 6:14-15).

The whole parable deals with repeated personal forgiveness and the reason for it. The King had already forgiven them much more than they could ever forgive their fellow disciples.

Immediately Jesus put the disciples in the position of servants (Gr. douloi) of a great king who is God. This is one of the relationships that disciples have to God that we must never forget. We are His servants as well as His sons.

Verses 24-27

This servant had great authority under an even greater king (cf. Matthew 18:1). However, he had amassed a debt of such huge proportions that he could not possibly repay it. A talent was a measure of weight equivalent to 75 pounds. The exact or even the relative buying power of 10,000 talents of silver is really secondary to the point Jesus was making, namely, that the debt was impossible to repay. Depending on the current price of silver, the slave owed the equivalent of many millions of dollars. There was no way he could begin to pay off such a debt.

"Ten thousand (myria, hence our ’myriad’) is the largest numeral for which a Greek term exists, and the talent is the largest known amount of money. When the two are combined, the effect is like our ’zillions.’" [Note: France, The Gospel . . ., p. 706.]

The king commanded that the servant sell everything he had to compensate him even though what he could pay amounted to a mere fraction of what he owed. The servant pleaded for time promising to repay everything, an obvious impossibility in view of the amount of the debt. Moved by compassion for the hopeless servant, the lord graciously cancelled the entire debt.

The Greek word for "debt" in Matthew 18:27 is daneion and really means "loan." Evidently the king decided to write off the indebtedness as a bad loan rather than view it as embezzlement, another indication of his grace.

Verses 28-31

The reaction of the forgiven servant was appalling. He proceeded to try to collect a debt from a fellow slave and even resorted to physical violence to obtain it. A denarius was a day’s wage for a common laborer or a foot soldier. [Note: Tobit 5:14; Tacitus Annales 1:17.] Therefore the debt owed was substantial, but compared with the debt the king had forgiven the creditor servant it was trivial.

Both debtors appealed to their respective creditors similarly (Matthew 18:26; Matthew 18:29). Yet the servant creditor remained unmoved, hardhearted. He threw his fellow servant into the debtor’s prison until he could extract the full amount of his debt from him. Other servants of the king, who were aware of the situation and deeply distressed by it, reported everything to their lord "in detail" (Gr. diesaphesan).

Verses 32-34

The king called the wicked servant into his presence and reminded him of the merciful treatment that he had received. It is interesting that the word he used for "debt" here is the usual word for debt, not "loan" as in Matthew 18:27. He took a different view of the servant’s debt now. Instead of forgiving him, the king turned the unforgiving servant over to the "torturers" (Gr. basanistais, cf. Matthew 18:6; Matthew 18:8-9). The servant would experience torture until he repaid his total debt, which he could never do. In other words his torment would be endless.

Verse 35

Jesus drew the crucial comparisons in applying the parable to His disciples. He pictured God as forgiving graciously yet punishing ruthlessly. God cannot forgive those who are devoid of compassion and mercy because He is so full of these qualities Himself. Jesus did not mean that people can earn God’s forgiveness by forgiving one another (cf. Matthew 6:12; Matthew 6:14-15). Those whom God has forgiven must forgive as God has forgiven them. This demonstrates true humility.

The idea of God delivering His servants, the disciples, over to endless torment has disturbed many readers of this parable. Some have concluded that Jesus meant a disciple can lose his salvation if he does not forgive. This makes salvation dependent on good works rather than belief in Jesus. Another possibility is that Jesus was using an impossible situation, endless torment, to warn His disciples. If the disciples knew it was an impossible situation, the warning would lose much of its force. Perhaps He meant that a disciple who does not genuinely forgive gives evidence that he or she has never really received God’s forgiveness. [Note: Pentecost, The Parables . . ., p. 67.] That person may be a disciple, but he or she is not a believer (cf. Judas Iscariot). However many genuine believers do not forgive their brethren as they should. Perhaps the punishment takes place in this life, not after death, and amounts to divine discipline (Matthew 18:14). [Note: Walvoord, Matthew: . . ., p. 140.] Another possibility is that Jesus had in mind a loss of eternal reward. Or perhaps this is simply another case of hyperbole to drive home a point.

Jesus concluded this discourse on humility, as He had begun it, with a reference to entering the kingdom (Matthew 18:3). Humility is necessary to enter the kingdom because it involves humbly receiving a gift of pardon from God (Matthew 18:27). However humility must continue to characterize the disciple. Not only must a disciple live before God as a humble child (Matthew 18:4). He or she must also be careful to avoid putting a stumbling block in the path of another disciple (Matthew 18:5-14). He or she must also humbly seek to restore a wayward fellow disciple (Matthew 18:15-20). Forgiving fellow disciples wholeheartedly and completely is likewise important for humble disciples (Matthew 18:21-35).

"His [Jesus’] message to the disciples is that loving concern for the neighbor and the spirit of forgiveness are to be the hallmarks of the community of believers in whose midst he, the Son of God, will ever be present." [Note: Kingsbury, Matthew as . . ., p. 79. Cf. Matthew 18:6; Matthew 18:10; Matthew 18:20-22.]

Bibliographical Information
Constable, Thomas. DD. "Commentary on Matthew 18". "Dr. Constable's Expository Notes". https://studylight.org/commentaries/eng/dcc/matthew-18.html. 2012.