So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, to day have I begotten thee. Christ glorified not himself - The man Jesus Christ, was also appointed by God to this most awful yet glorious office, of being the High Priest of the whole human race. The Jewish high priest represented this by the sacrifices of beasts which he offered; the Christian High Priest must offer his own life: Jesus Christ did so; and, rising from the dead, he ascended to heaven, and there ever appeareth in the presence of God for us. Thus he has reassumed the sacerdotal office; and because he never dies, he can never have a successor. He can have no vicars, either in heaven or upon earth; those who pretend to be such are impostors, and are worthy neither of respect nor credit.
Thou art my Son - See on Hebrews 1:5 (note), and the observations at the end of that chapter. And thus it appears that God can have no high priest but his Son; and to that office none can now pretend without blasphemy, for the Son of God is still the High Priest in his temple.