John Chrysostom

And after that he did not simply pass on, but added, "and blessed him that had the promises." Inasmuch as throughout, this was regarded with reverence, he shows that Melchisedec was to be reverenced more than Abraham, from the common judgment of all men. "And without all contradiction," he says, "the less is blessed of the better," i.e. in the opinion of all men it is the inferior that is blessed by the superior. So then the type of Christ is superior even to "him that had the promises."

Homily on Hebrews 12 ↗

Theophylact of Ohrid

The Apostle said that Melchizedek blessed so great an Abraham. Yet we all agree without dispute that the one who blesses is greater than the one who is blessed. Therefore, Melchizedek too, the prototype of Christ, is greater than the patriarch.

Commentary on Hebrews ↗

Oecumenius

"But he whose genealogy is not counted among them." Among them, that is, among those. Therefore, he whose genealogy is not mentioned to among them, nor reckoned in the number with their kind, namely Melchizedek, received tithes. "and blessed the one who has the promises. He took up Abraham, so that Melchizedek might receive more. …

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

343. – Then when he says, it is beyond dispute that the inferior is blessed by the superior, he states the major premise of his reasoning. But here there are three objections: the first concerns the statement that the lesser is blessed by the better. On this score the Poor Men of Lyons claim that any just person is greater than a sinner; consequently, a just layman is not blessed by a wicked priest, but conversely. Hence, they would have it that every just man is a priest and no sinner is a priest. …

Commentary on Hebrews ↗