The parable of the unforgiving servant is realistic and strange. It is realistic that a king would settle accounts. It is strange that he would demand that the debtor's family also be enslaved, much less sold! Jewish law stipulated that only the debtor be enslaved, not that his family be enslaved or sold. This exaggeration is meant to underscore the harshness and mercilessness of the king.
It is strange that a servant would owe such a massive amount as 10,000 talents, an amount that could never be repayable in one lifetime, since 1 talent was the equivalent of 15-20 years of daily wages. The absurd amount highlights how tremendously grateful the first servant should be to the king for the forgiveness of such a massive debt. The monumental amount the first servant owed the king also is meant to contrast with the relatively modest amount that the second servant owes the first servant. The amount is 100 denarii. A denarius is the equivalent of one day's wages, so this is certainly an amount that can be repaid in a timely fashion (Donahue, 75).
The cruelty of the king reminds us of other violent overreactions by authority figures elsewhere in Matthew's Gospel: the king in the parable of the wedding garment (Matthew 22:12) and the master in the parable of the talents (25:30). These sorts of reactions are missing from the parables unique to Luke.
So we have a picture here of a terribly harsh king who, inexplicably, takes pity on a servant who owes him a tremendous debt. And we have a picture of a person who has been shown tremendous mercy, inexplicably unwilling to extend it to someone else.
What motivates someone who is apparently without pity to take pity? What motivates a person who has been shown mercy to deny it to someone else?
Do we see ourselves in either of those questions? Do we need, in our lives, in our relationships, Matthew's reminder that, in light of the coming reckoning, we need to make changes in the way we do things?
Paul S. Duke, The Parables (Abingdon Press, 2005).
John R. Donahue, The Gospel in Parables (Fortress Press, 1988).