Gregory the Dialogist

Hence it is fittingly added: "Or is your eye evil because I am good?" But let no one exalt himself on account of his work, let no one exalt himself on account of time, since with this statement completed, the Truth subsequently cries out: "So the last shall be first, and the first last." For behold, even if we already know what and how great the good things we have done are, we still do not know with what subtlety the heavenly Judge examines these things. …

Forty Gospel Homilies, Homily 19 ↗

Thomas Aquinas

On the contrary, he says, or is it not lawful for me to do what I will? Because it is lawful for anyone to do his will with what is his own. For if he were a debtor to another, it would not be lawful for him to do so; likewise, if he were under another; but he is the Lord, and therefore he can give more. For a steward cannot give anything except according to merits; but a king can give without merits. So God, who is Lord of all, can do so. Psalm 113:11: he has done all things whatsoever he willed. Romans 9:19: who resists his will? …

Commentary on Matthew ↗

Remigius of Rheims

By the eye is understood his purpose. The Jews had an evil eye, that is, an evil purpose, seeing they were grieved at the salvation of the Gentiles.

Catena Aurea by Aquinas ↗