If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron? If therefore perfection were by the Levitical priesthood - The word τελειωσις, as we have before seen, signifies the completing or finishing of any thing, so as to leave nothing imperfect, and nothing wanting. Applied here to the Levitical priesthood, it signifies the accomplishment of that for which a priesthood is established, viz.: giving the Deity an acceptable service, enlightening and instructing the people, pardoning all offenses, purging the conscience from guilt, purifying the soul and preparing it for heaven, and regulating the conduct of the people according to the precepts of the moral law. This perfection never came, and never could come, by the Levitical law; it was the shadow of good things to come, but was not the substance. It represented a perfect system, but was imperfect in itself. It showed that there was guilt, and that there was an absolute need for a sacrificial offering to atone for sin, and it typified that sacrifice; but every sacrificial act under that law most forcibly proved that it was impossible for the blood of Bulls and Goats to take away sin.
For under it the people received the law - That is, as most interpret this place, under the priesthood, ἱερωσυνῃ being understood; because, on the priesthood the whole Mosaical law and the Jewish economy depended: but it is much better to understand επ' αυτῃ on account of it, instead of under it; for it is a positive fact that the law was given before any priesthood was established, for Aaron and his sons were not called nor separated to this office till Moses came down the second time from the mount with the tables renewed, after that he had broken them, Exodus 40:12-14. But it was in reference to the great sacrificial system that the law was given, and on that law the priesthood was established; for, why was a priesthood necessary, but because that law was broken and must be fulfilled?
That another priest should rise - The law was given that the offense might abound, and sin appear exceeding sinful; and to show the absolute necessity of the sacrifice and mediation of the great Messiah, but it was neither perfect in itself, nor could it confer perfection, nor did it contain the original priesthood. Melchisedec had a priesthood more than four hundred years (422) before the law was given; and David prophesied, Psalms 110:4, that another priest should arise after the order of Melchisedec, nearly five hundred years (476) after the law was given. The law, therefore, did not contain the original priesthood; this existed typically in Melchisedec, and really in Jesus Christ.