So the former commandment is set aside because it was weak and useless
18. For there is verily a disannulling, or abrogation, etc. As the Apostle’s discourse depends on this hinge, that the Law together with the priesthood had come to an end, he explains the reason why it ought to have been abolished, even because it was weak and unprofitable.
Observe the necessity there was of raising up another priest, after the order of Melchisedec and not after the order of Aaron, by whom that perfection should come which could not come by the Levitical priesthood, which therefore must be changed, and the whole economy with it, Heb 7:11, Heb 7:12, etc. Here, I. It is asserted that perfection could not come by the Levitical priesthood and the law.
Commenting on Hebrews 7:11-28
For the law made nothing perfect,.... Or no man; neither any of the priests that offered sacrifices, nor any of the people for whom they were offered: it could not perfectly make atonement for sin; nor make men perfectly holy or righteous; it could neither justify nor sanctify; neither bring in a perfect righteousness, nor bring men to perfect holiness, and so to eternal life...