Matthew Poole and continuators on Hebrews 7:4

4 Now consider how great this man was , unto whom even the patriarch Abraham gave the tenth of the spoils .

The Spirit compares with, and prefers Melchisedec before Abraham, as he was God's High Priest; he introduces it with pressing these Hebrews to exercise an act of Judgment under the Metaphor of seeing, denoting it to be such a serious and intent act, as calls for the utmost Exercise of the discerning Faculty; a Carelesness in it, or an Oversight might make the Proposal to be to no purpose. The Greatness of this High-Priest is what he sets in their View, and that indefinitely, How great is this Officer? intimating him to be somewhat excessive to other great ones; and how much greater then must be Christ, if his Type be so great beyond, not only Abraham, Levi, and his Posterity, but this great Melchisedec, as to his Sacerdotal Power and Dignity.

This Greatness is evinced by Abraham's (the Patriarch, chief of all the Fathers of Israel, whom the Hebrews esteemed above all others, Iohn 8.53. and God owns as his Friend, and sets all Believers under his Fatherhood) giving, as a due to Melchisedec, being the greater Person in Office, the Tenth of all the Spoils, that which was due to God, and paid to him as God's High Priest; [non-Latin text not transcribed] notes either the first or choisest of the heaps of Grains, especially the first-Fruits dedicated to God; but here signifieth that part of the Spoils, which, according to the custom of War in most Nations after the Victory, were offered to God as his part; whether they did consist of Persons or Things; the tenth part of these were given by him to Melchisedec as the greatest Priest of God in the World, and superior to himself.

Marginal references: Gen. 14.20.