Parable of the Unmerciful Servant
Then Peter came to Jesus and asked, “Lord, how many times shall I forgive my brother when he sins against me? Up to seven times?” Jesus answered, “I tell you, not seven times, but seventy-seven times. Matthew 16:21-22
This parable comes after a discourse on how to discipline a believer, but the parable explains that a requirement of following Jesus is forgiveness; the capacity for repeated, personal, forgiveness.
A man has built up a massive and unpayable debt of 10,000 talents; that's the amount that King David gave to help rebuild the Temple! The man could never pay this even by going into slavery.
In the parable, the King takes pity on him and cancels the debt. But the man goes away and refuses to be lenient to a servant of his who owes him around about 100 days salary. He has failed to forgive in the way that he himself has been forgiven and so in the parable he ends up being tortured!
Those of us in the Kingdom of God serve a King who has forgiven us much more than we can ever forgive each other. If we fail to forgive, we face exclusion from the Kingdom. Because God is full of compassion and grace and mercy, He cannot accept those who refuse to exhibit the same Kingdom compassion and forgiveness. Those who are forgiven must forgive!