John Calvin Commentary Hebrews 7:6

"but he whose genealogy is not counted from them hath taken tithes of Abraham, and hath blessed him that hath the promises." — Hebrews 7:6 (ASV)

Blessed him, etc. This is the fifth comparison between Christ and Melchizedek. The Apostle assumes it as an accepted principle that the lesser is blessed by the greater; and then he adds that Melchizedek blessed Abraham. Therefore, the conclusion is that Abraham was the lesser. However, to strengthen his argument, he again emphasizes Abraham's dignity, because the more glorious Abraham is made, the higher Melchizedek's dignity appears.

For this purpose, he says that Abraham had the promises; by which he means that Abraham was the first of the holy race with whom God made the covenant of eternal life. Indeed, it was no common honor that God chose him from all others to entrust to him the privilege of adoption and the testimony of His love.

Yet, all this did not prevent him, in all his preeminence, from submitting himself to the priesthood of Melchizedek. Thus, we see how great Melchizedek was, to whom Abraham yielded in these two respects: he allowed himself to be blessed by him, and he offered him tithes as to God’s vicegerent.