Jerome

But if he who handed over the innocent blood sinned, how much more did the Jews sin, who bought the innocent blood, and by offering a price, provoked the betrayal of the disciple? Let those who attempt to introduce different natures and say that Judas, the traitor, had an evil nature, and could not be saved by election, answer how an evil nature could have repented.

Commentary on Matthew ↗

Leo the Great

When he says, I have sinned, in that I have betrayed innocent blood, he persists in his wicked treachery, seeing that amid the last struggles of death he believed not Jesus to be the Son of God, but merely man of our rank; for had he not thus denied His omnipotence, he would have obtained His mercy.

Catena Aurea by Aquinas ↗

Thomas Aquinas

Next follows the effect. The effect of repentance is that the sinner strive to make amends. He had sinned because he had sold Christ, for he had done what was in his power: therefore he brought back the thirty denarii. And first, the retraction is set forth; secondly, the repentance, at "I have sinned in betraying just blood." He brought back, therefore, the thirty pieces of silver; and in this he retracted, saying "I have sinned," i.e., I have truly done wrong. …

Commentary on Matthew ↗