The servant is forgiven his debt to his master. Why? Compassion. The master knows what it is to suffer under the burden of debt. Freed from his debt, the forgiven-servant refuses to forgive the debt of a fellow servant. Why? Greed. Power. Arrogance. Who knows?
All we know is that he did not show his fellow servant the same compassion shown to him. This failure to “pass on” the gifts of compassion dooms the forgiven-servant to the tools of the torturers. Notice: the forgiven-servant is forgiven, yet he ends up on the rack, suffering despite his state of apparent grace. He loses his status as forgiven as soon as he fails to measure another with the same measure used to measure him.
Forgiveness empowers forgiveness. It's infectious. Refusing to infect another with mercy is nothing more than obstinate negligence. And that refusal is damning. If the threat of torturers is not enough to open a heart to mercy, then perhaps knowing that being a creditor to a broken soul makes that heart a debtor to God. His compassion is infinite. But is there room in this debtor's heart to receive all that the Father freely offers?