Theophylact of Ohrid

And his lord was wroth, and delivered him to the tormentors, till he should pay all his debt. To what tormentors does he deliver him? To the punitive powers for eternal punishment. For the meaning of "till he should pay all his debt" is this: "let him be punished till that he should pay all that was due." But he will never be able to pay his debt, and therefore his punishment will never end.

Commentary on Matthew ↗

Thomas Aquinas

And his lord being angry, etc. And first he treats of the punishment, through which separation from God occurs. When above the Lord commanded that he be sold, he did not say that he was angry, because admonitions are not from divine justice, but from mercy; but the reproach is from the anger of God. Prov 19:12: as the roaring of a lion, so also is the anger of the king. Secondly, because he is subjected to demons; hence he delivered him to the torturers. Sir 33:14: he will repay them according to his judgment. …

Commentary on Matthew ↗

Remigius of Rheims

For God is said then to be wroth, when he takes vengeance on sinners. Torturers are intended for the daemons, who are always ready to take up lost souls, and torture them in the pangs of eternal punishment. Will any who is once sunk into everlasting condemnation ever come to find season of repentance, and a way to escape? Never; that until is put for infinity; and the meaning is, He shall be ever paying, and shall never quit the debt, but shall be ever under punishment,

Catena Aurea by Aquinas ↗