What does Matthew 18:28 mean?

Those engaged in Jesus' parable have likely breathed a sigh of relief. He depicted a servant who owed the king an impossible amount of money. The king was going to exercise his right to sell the man and the man's family into slavery as a payment on that debt. The servant begged for time to pay the debt off, something he clearly could never do since it was such a large amount. Then, finally, the king graciously forgave the man for the entire amount of the debt with no need to ever pay it back (Matthew 18:23–27).

The man was free. It was a story with a happy ending. For those with ears to hear (Mark 4:9), this part of the story gives perspective to humanity's relationship with a forgiving God. Through faith in Christ, God forgives a debt for our sin that we could never hope to repay. That debt is so severe it's remarkable God allowed us to fall so far in the first place. We deserve eternal fire, and God gives us instead an eternal place in His own family through faith in Christ (Romans 5:8; John 1:12; 3:16–18).

This story is not over, though. Jesus continues, following the man out from the presence of the king and into a confrontation with another servant. This fellow servant owes the man 100 denarii. This is not a tiny sum; a denarius was about a days' wages. Still, it was an irrelevant fraction of a fraction of a percent of what the king had just forgiven this man. All the same, the man angrily demands payment, grabbing the other servant and even choking him.