John Chrysostom

"But he whose descent is not counted from them, received tithes of Abraham." 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.

Homily on Hebrews 12 ↗

Theophylact of Ohrid

Hence Melchizedek too, who received a tithe from Abraham, and moreover not being of his lineage, for he was a foreigner, is superior and higher than he. For why would Abraham have given a tithe to a foreigner if great honor did not belong to him? And if Melchizedek, the type, surpasses even Abraham himself, how much more does the true High Priest surpass the priests of the law. …

Commentary on Hebrews ↗

Oecumenius

"who have come out." This is what it says: Although in all other respects they were equal in condition and honor, yet from the fact that these indeed gave tithes, while those received them, great excellence is shown. If this is so, it is clear that even in Abraham and Melchizedek, when Abraham gave tithes, Melchizedek received them. Therefore, he who was a type and figure of Christ was greater than the patriarch Abraham: and if Abraham himself, much more the priests. But if the type was greater, what can anyone say about Christ?

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

341. – Then when he says, But this man who has not the genealogy received tithes of Abraham, he shows how it was more fitting for Melchizedek to receive tithes, because he was not of the stock of Abraham; hence, he has not their genealogy, namely, of the Levites. Furthermore, according to a commandment of the Law it was lawful for him to take tithes; consequently, their priesthood was subject to the observance of the Law. …

Commentary on Hebrews ↗