John Calvin Commentary Genesis 14:19

"And he blessed him, and said, Blessed be Abram of God Most High, possessor of heaven and earth:" — Genesis 14:19 (ASV)

And he blessed him. Unless these two parts of the sentence, ‘He was the priest of God,’ and ‘He blessed,’ cohere, Moses here relates nothing uncommon. For people mutually bless each other; that is, they wish well to each other. But here the priest of God is described, who, according to the right of his office, sanctifies one inferior and subject to him. For he would never have dared to bless Abram unless he had known that in this respect he excelled him.

In this manner, the Levitical priests are commanded to bless the people; and God promises that the blessing should be efficacious and ratified (Numbers 6:23). So Christ, when about to ascend to heaven, having lifted up His hands, blessed the Apostles as a minister of the grace of God (Luke 24:51); and then the truth of this figure was exhibited. For He testifies that the office of blessing the Church, which had been foreshadowed in Melchizedek, was assigned to Him by His Father.

Blessed be Abram of the Most High God. Melchizedek’s purpose is to confirm and ratify the grace of the divine vocation to holy Abram; for he points out the honor with which God had uniquely dignified him by separating him from all others and adopting him as His own son.

And he calls God, by whom Abram had been chosen, the Possessor of heaven and earth, to distinguish Him from the fictitious idols of the Gentiles. Afterwards, indeed, God assumes other titles. He does this so that, by some distinctive mark, He may make Himself more clearly known to people. For when people, because of the vanity of their mind, simply hear of God as the Creator of heaven and earth, they never cease to wander until finally they are lost in their own speculations.

But because God was already known to Abram, and his faith was founded upon many miracles, Melchizedek considers it sufficient to declare that, by the title of Creator, He whom Abram worshipped is the true and only God. And although Melchizedek himself maintained the sincere worship of the true God, he nevertheless calls Abram blessed by God with respect to the eternal covenant: as if to say that, by a kind of hereditary right, the grace of God resided in one family and nation, because Abram alone had been chosen out of the whole world.

Then a special congratulation on the victory obtained is added; not the kind that usually passes between worldly people, who puff each other up with inflated praises; but Melchizedek gives thanks to God and regards the victory which the holy man had gained as a seal of his gratuitous calling.