John Calvin Commentary Hebrews 7:18

"For there is a disannulling of a foregoing commandment because of its weakness and unprofitableness" — Hebrews 7:18 (ASV)

For there is verily a disannulling, or abrogation, etc. Since the Apostle’s discourse hinges on the fact that the Law, along with the priesthood, had come to an end, he explains the reason why it should have been abolished: because it was weak and unprofitable.

He speaks this way in reference to the ceremonies, which had nothing substantial in them, nor did they, in themselves, offer anything for salvation. For the promise of favor connected with them, and what Moses everywhere testifies—that God would be appeased by sacrifices and that sins would be atoned for—did not properly belong to the sacrifices themselves, but were only added to them.

For just as all types referred to Christ, so from Him they derived all their power and effect. Indeed, of themselves they achieved nothing and accomplished nothing; their whole effectiveness depended on Christ alone.

But since the Jews foolishly set these ceremonies up in opposition to Christ, the Apostle, addressing this notion, shows the difference between these things and Christ. For as soon as they are separated from Christ, nothing is left in them but the weakness he speaks of. In short, no benefit is to be found in the ancient ceremonies unless they refer to Christ, for in this way they made the Jews acquainted with God’s grace to such an extent that they, in a way, kept them in expectation of it.

Let us then remember that the Law is useless when separated from Christ.

He also confirms this same truth by calling it the commandment going before; for it is a well-known and common saying that former laws are abrogated by later ones. The Law had been promulgated long before David; but David was in possession of his kingdom when he proclaimed this prophecy concerning the appointment of a new priest. This new Law then annulled the former.