Thomas Aquinas

Likewise, from his cruelty, because he was unwilling to forgive. Hence first the supplication of the debtor is presented; secondly, his cruelty, at but he would not, etc. Note that all the things that the first servant did before the Lord, this one did before him; hence falling down he besought him. Above it says he prayed, here he besought, because above he rendered the honor due to God; but here it is the honor due to man: therefore it says he besought.

Commentary on Matthew ↗