11 Therefore, if perfection were through the Levitical priesthood (for under it the people received the law), what further need was there that another priest should rise according to the order of Melchizedek, and not be called according to the order of Aaron? 12 For the priesthood being changed, of necessity there is also a change of the law.
Having established that Melchizedek was superior to Abraham and the Levitical priesthood, Hebrews now shows how Jesus’ priesthood is supreme over all other priesthoods. It is not only supreme, but it supersedes the Levitical priesthood (He 7:11-19)
The next verses conclude the argument of the first 10. The entire Mosaic ceremonial law and Levitical priesthood came to an end when Christ came.
if [contrary to the fact] perfection [completion]
In the Greek the “if” clause is contrary to the fact (second class condition). The Levitical priesthood did not secure completion of its purpose; it could not redeem people but only pointed to the One who would. The law made nothing perfect (He 7:19). The law could only atone for sin (cover sin) but Jesus eradicated it.
The theme of “perfection” or completion frames Christ’s priesthood. “Perfection” is the condition under which people are acceptable to God. His is superior to Levitical priesthoods. There would be no need for a different priest if the Levitical system were perfect or complete. That system could typify but not fulfill; it could not finish the issue of sacrifice for sin.
were through the Levitical priesthood (for under it the people received the law),
The Levitical priesthood was given in association with the Mosaic law.
what further need was there that another priest [Jesus] should rise
There was a need for a new order of priesthood because the old was not perfect or complete (He 8:7; Ro 6:14). The essential point is that a change in the priesthood created a need for this new order of priesthood. If the Levitical priesthood would have been sufficient, it would have been meaningless to speak of another priesthood of a different order. The older order needed to be superseded by a new order.
according to the order of Melchizedek,
Christ superseded the Mosaic Levitical priesthood by the Melchizedekian order of priesthood (Ps 110:4). The priesthood of Christ was of a higher order.
and not be called according to the order of Aaron?
Aaron was the first priest under the law. Levi was the family chosen to be priests. Jesus’ priesthood did not come from the lineage of the Levitical priesthood. That had to be replaced because it did not bring to completion (“perfection”) the need for a fulfilled or completed sacrifice.
For the priesthood being changed [transposed],
The word “changed” means to put one thing in the place of another. Since the Mosaic ceremonial law was superseded there is a need for a new priesthood to replace the Levitical priesthood. Christianity did not enhance Judaism but replaced it. A change in one is a change in the other.
of necessity there is also a change of the law.
There was a change in the Mosaic law when Christ came (He 7:16-28; Ga 3:24). The law had to change when Christ’s priesthood superseded the type for the antitype. The ceremonial functions of the Levitical priesthood were abrogated. Our Lord disannulled not only the Levitical priesthood but the entire ceremonial Mosaic system because they are linked hand-in-hand.
Many converted Jews at the writing of Hebrews still clung to the institutions and ceremonies of the Mosaic law. They needed to understand that the Antitype was not an appendage to the law; it was a radically new and different entity. The two are mutually exclusive; they cannot be blended.
Christians today do not live under the law but grace.
If the law was not done away for Christians today, then neither was the Levitical priesthood. If Christ is our High Priest, then we cannot be under the law. God terminated the ceremonial law (the type) when Christ the Antitype came (Ro 10:4). Christians are therefore not under the law (Ro 6:14-15; Ga 3:24-25; 5:1; 6:2; 2 Co 3:7-11). We live under an entirely different system of operation than the law; we live under the principle of grace (Ro 11:6).