What does Matthew 18:27 mean?

After teaching that Christians should plan to offer unlimited forgiveness (Matthew 18:21–22), Jesus is illustrating with a parable. A servant owes his king 10,000 talents—each talent being worth twenty years of labor. This would have been an impossible amount to imagine a servant owing to a king. It's certainly a sign of the king's patience to allow that to happen (Romans 2:4). Since the servant cannot pay, the king has ordered that he and his family be sold into slavery to make some payment (Matthew 18:23–25).

The servant has begged the king to be patient, promising to pay back all he owes. This, obviously, would have been impossible (Matthew 18:26).

This leads to an unexpected twist: The king takes pity on the man. He doesn't set up a payment plan. He doesn't cut the debt in half. In pity for his servant, the king simply forgives the entire amount. He wipes out the debt. It is gone. If it was impossible to imagine owing a king that amount of money, it would have likely been even more impossible for Jesus' listeners to imagine a king just forgiving it. The king in Jesus' story, though, does exactly that.

The meaning behind Jesus' parable is taking shape, and some of His first listeners may have begun to think they understood it. The debt of sin was apparently often compared to financial debts during this time. Here is a powerful king who not only patiently stands by while a servant accumulates mind-boggling debt, he then forgives the debt. This is meant to be a powerful analogy for salvation through faith in Christ (Romans 5:8; Titus 3:5).

The parable is not done, however. Peter's initial question was about being forgiving towards other people, and so far Jesus has only spoken of forgiveness granted by a king. The tie-in to Peter's question comes in the next part of the story (Matthew 18:28).