Forgiveness is such a fundamental teaching of Jesus that when He was preparing His disciples to send them out into the world to preach the Gospel He said "This is what is written: The Christ will suffer and rise from the dead on the third day, and repentance and forgiveness of sins will be preached in his name to all nations" (Luke 24:47). So "the Gospel of the Kingdom" or what Paul later called "the Gospel of Grace" was the Gospel of repentance and forgiveness.
Yet God's forgiveness was not new or unique to the teachings of Jesus. In the Old Testament we find it is in the nature of God that He is "a God forgiving iniquity and transgression and sin" (Ex 34:7, and many others like it). We find many prayers for forgiveness in the OT. Yet His forgiveness is never automatic and on occasions He refused to forgive and the prophets even asked that sometimes God would not forgive (Isa 2:9; Jer 18:23).
What we find in the teachings of Jesus is a shift in the way people are forgiven. The scribes were indignant that Jesus forgave sins (Mark 2:7) because the OT taught that God alone can forgive sins. But this wasn't the only thing about Jesus' teaching on forgiveness that was radical. Jesus also taught that God's forgiveness cannot be effectively received except by those who are ready to forgive others.
- "Forgive us our debts, as we also have forgiven our debtors ... For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins." (Matt 6:12-15)
This is not to say that our readiness to forgive someone can be regarded as a meritorious precondition for God's forgiveness, but rather that forgiveness of others is a characteristic of the new life in Christ and is a daily sign of the forgiven sinner's gratitude.
In the parable of the two debtors (Matt 18:23-35) Jesus' final comment makes it clear that the remission of a debt is a parable of forgiveness in the kingdom of heaven and that through the Kingdom which Jesus inaugurated God's rule has already been established in a new way. Forgiveness is still initiated by God but it now extends to the community of God's people - His Kingdom - whose members are to forgive one another without limit (Matt 18:22; Luke 17:3-4).
The normal NT verb for "forgive" is aphiemi, and the noun is aphesis. While Paul uses this word a few times he more often uses a different word - charizomai (which is connected with charis, grace) - which means to "give freely or graciously as a favour". He uses this word in the sense of "forgive" to bring out the truth that Christians ought to be forgiving people. For example, when writing about a man who has been punished enough he says "you should forgive (charizomai) and comfort him" (2 Cor 2:6-7). The motivation for this is spelled out in Col 3:13: "forgive whatever grievances you may have against one another. Forgive as the Lord forgave you."
In two of his speeches in Acts Paul says that forgiveness is the climax of the Gospel.
- "Therefore, my brothers, I want you to know that through Jesus the forgiveness of sins is proclaimed to you." (Acts 13:38)
- Jesus said to Paul: "I am sending you to them [the Gentiles] to open their eyes and turn them from darkness to light, and from the power of Satan to God, so that they may receive forgiveness of sins and a place among those who are sanctified by faith in me." (Acts 26:17-18)
The Gospel of the Kingdom is the Gospel of grace, the Gospel of forgiveness. It is preached not only be teaching about God's forgiveness which is freely given , but through a demonstration of forgiveness by a forgiven people who reflect what God has done for them by then doing it for others.