Albert Barnes on Matthew 18:27

The lord of that servant was moved with compassion, etc. He had pity on him. He saw his distressed condition. He pitied his family. He forgave him the whole debt. This represents the mercy of God to men. They had sinned. They owed to God more than could be paid. They were about to be cast off. But God has mercy on them, and in conexion with their prayers, forgives them. We are not to interpret the circumstances of a parable too strictly. The verse about selling the wife and children is not to be taken literally, as if God was about to punish them for the sins of their father; but it is a circumstance thrown in to keep up the story; to make it consistent; to explain why the servant was so anxious to obtain a delay of the time of payment.

(v) "loosed him" Ps 78:38