14:17-20 Melchizedek is spoken of as a king of Salem, supposed to be the place afterwards called Jerusalem, and it is generally thought that he was only a man. The words of the apostle, Heb 7:3, state only, that the sacred history has said nothing of his ancestors. The silence of the Scriptures on this, is to raise our thoughts to Him, whose generation cannot be declared. Bread and wine were suitable refreshment for the weary followers of Abram; and it is remarkable that Christ appointed the same as the memorials of his body and blood, which are meat and drink indeed to the soul. Melchizedek blessed Abram from God. He blessed God from Abram. We ought to give thanks for other's mercies as for our own. Jesus Christ, our great High Priest, is the Mediator both of our prayers and praises, and not only offers up ours, but his own for us. Abram gave him the tenth of the spoils, Heb 7:4. When we have received some great mercy from God, it is very fit we should express our thankfulness by some special act of pious charity. Jesus Christ, our great Melchisedek, is to have homage done him, and to be humbly acknowledged as our King and Priest; not only the tithe of all, but all we have, must be given up to him.
20. he gave him tithes of all—Here is an evidence of Abram's piety, as well as of his valor; for it was to a priest or official mediator between God and him that Abram gave a tenth of the spoil—a token of his gratitude and in honor of a divine ordinance (Pr 3:9).