Albert Barnes Commentary Hebrews 7:11

"Now if there was perfection through the Levitical priesthood (for under it hath the people received the law), what further need [was there] that another priest should arise after the order of Melchizedek, and not be reckoned after the order of Aaron?" — Hebrews 7:11 (ASV)

If therefore perfection were by the Levitical priesthood. As the Jews supposed. They were accustomed to regard the system as perfect. It was an appointment of God, and they were tenacious of the opinion that it was to be permanent and needed no change. But Paul says that this could not be. Even from their own Scriptures, it was apparent that a priest was to arise of another order and of a more permanent character. This, he says, was full proof that there was defect of some kind in the previous order.

What this defect was he does not specify here, but the subsequent reasoning shows that it was in such points as these: it was not permanent; it could not make the worshippers perfect; the blood they offered in sacrifice could not take away sin and could not render those who offered it holy. (Compare to Hebrews 7:19, 23, 24; Hebrews 10:1–4).

For under it the people received the law. This assertion seems necessary to establish the point maintained in Hebrews 7:12, that if the priesthood is changed, there must also be a change of the law. For this, it was necessary to admit that the law was received under that system and that it was a part of it, so that the change of one involved the change of the other.

It was not strictly true that the whole law was given after the various orders of Levitical priests were established—for the law on Sinai and several other laws were given before that distinct arrangement was made—but it was true:

1. that a considerable part of the laws of Moses were given under that arrangement; and
2. that the whole of the ceremonial observances was connected with that.

They were parts of one system and mutually dependent on each other. This is all that the argument demands.

What further need was there, etc.? "If that system would lead to perfection, if it was sufficient to make the conscience pure and to remove sin, then there was no necessity of any other. Yet the Scriptures have declared that there would be another of a different order, implying that there was some defect in the former."

This reasoning is founded on the fact that there was an express prediction of the coming of a priest of a different "order" (Psalms 110:4), and that this fact implied that there was some deficiency in the former arrangement. To this reasoning, it is impossible to conceive that there can be any objection.