Matthew 18:23-35
23 Therefore is the kingdom of heaven likened unto a certain king, which would take account of his servants.
24 And when he had begun to reckon, one was brought unto him, which owed him ten thousand talents.
25 But forasmuch as he had not to pay, his lord commanded him to be sold, and his wife, and children, and all that he had, and payment to be made.
26 The servant therefore fell down, and worshipped him, saying, Lord, have patience with me, and I will pay thee all.
27 Then the lord of that servant was moved with compassion, and loosed him, and forgave him the debt.
28 But the same servant went out, and found one of his fellowservants, which owed him an hundred pence: and he laid hands on him, and took him by the throat, saying, Pay me that thou owest.
29 And his fellowservant fell down at his feet, and besought him, saying, Have patience with me, and I will pay thee all.
30 And he would not: but went and cast him into prison, till he should pay the debt.
31 So when his fellowservants saw what was done, they were very sorry, and came and told unto their lord all that was done.
32 Then his lord, after that he had called him, said unto him, O thou wicked servant, I forgave thee all that debt, because thou desiredst me:
33 Shouldest not thou also have had compassion on thy fellowservant, even as I had pity on thee?
34 And his lord was wroth, and delivered him to the tormentors, till he should pay all that was due unto him.
35 So likewise shall my heavenly Father do also unto you, if ye from your hearts forgive not every one his brother their trespasses.
The Grace New Testament Commentary - Matthew 18:31-35
18:31-34 The king, who had forgiven the first servant, heard how unforgiving the first servant had acted. In anger he held the first servant accountable for his refusal to forgive, calling him a "wicked servant." The king meted out the severe punishment the servant deserved for his lack of forgiveness. He handed the unforgiving servant over to his torturers until the man repaid "all that was due to him," which, of course, could never be repaid. The extent of his punishment matched his wickedness. The court-appointed torturers demanded excessive labor, deprived their prisoners of needful rest or food, and inflicted bodily and mental pain.
What does the torture signify? Some say handing him over to torturers is talking about purgatory, but the Bible knows of no such place. Nor is the deliverance to the torturers depicting eternal punishment in hell. The first servant in the parable actually experienced forgiveness. It is clear that the application of the warning pertains to believers (i.e., you [plural], pertaining to Peter, but also the other disciples who were with him, in v 35).
Instead, the deliverance "to the torturers" is indicative of the severity of the divine discipline that falls on an unforgiving child of God in this life (1 Cor 11:30-32; Heb 12:5-11). While a Christian's sins will be forgiven and forgotten forever (Heb 8:12; 10:14-17), he will be held accountable for failing to show the same forgiveness God has shown Him. The debt is remembered at another level - a level dealing with the Christian's practice, not his position in Christ (cf. 1 John 1:9 with Col 1:14; 2:13-14). God will not extend temporal forgiveness to unforgiving Christians. They will experience His displeasure so long as they remain unrepentant.
18:35 The parable answers a question Peter could have asked, but did not: "What happens if I don't forgive to the same extent I have been forgiven?" The answer in both the parable and in this verse is that God will hold accountable one who refuses to "forgive his brother his trespasses." One who has been forgiven by God of everything is obligated to forgive others too. The lesson of this aspect of the parable is, "Do not expect God to deliver you from the temporal consequences of your daily sins if you refuse to forgive others their sins."