“For the priesthood being changed, of necessity there is also a change of the law” (Hebrews 7:12).
In Romans 6:14 we read, “For sin shall not have dominion over you, for you are not under law but under grace.” Hebrews 7:12 clarifies that passage in helping to explain why we are no longer under the law.
To begin, we should recognize that there are three aspects to the Old Testament law: civil, ceremonial, and moral. The civil law defined lawful and unlawful activities and various types of contractual arrangements for the people of ancient Israel. The ceremonial law prescribed the manner in which sinful human beings could approach God under the Old Covenant sacrificial system. The moral law explained the difference between right and wrong.
In changing the arrangement through which human beings could approach their Creator, the ceremonial law had to be modified to accommodate that change. Since a new High Priest from outside the Levitical priesthood had come as a result of God’s promise, the priestly order also underwent a change. Under the old covenant, a human priest presided over the death of a sacrificial animal to atone for the sins of others. Under the new covenant, the High Priest sacrificed Himself to atone for the sins of others.
So what purpose did the Law serve? Well, the New Testament letter to the Galatians supplies the answer…
“Therefore the law was our tutor to bring us to Christ, that we might be justified by faith. But after faith has come, we are no longer under a tutor” (Galatians 3:24-25).
The Biblical book of Romans adds…
“For Christ is the end of the law for righteousness to everyone who believes” (Romans 10:4).
One source expands upon this idea as it relates to our passage from Hebrews 7:12…
“This verse is one of the clearest single statements in the New Testament indicating that God had terminated the Mosaic Law (Covenant; cf. Rom. 10:4)… Paul went on to say that Christians, therefore, are not under the Law (Rom. 6:14-15; Gal. 3:24-25; 5:1; 6:2; 2 Cor. 3:7- 11). That is, the Mosaic Covenant is not what God has given to regulate the lives of Christians.” (1)
Finally, it’s important to note that we still carry a moral obligation to honor God in our personal conduct, even though we are no longer under the civil and ceremonial requirements given to us in the Old Testament Law. Since the Law provides us with the knowledge of sin (Romans 3:20), the general moral principles we find there are just as valid today as they were when they were originally written.
(1) Constable, Thomas. DD, Notes on Hebrews 2022 Edition “The imperfection of the Levitical priesthood and the Mosaic Law 7:11-14” [7:12] https://www.planobiblechapel.org/tcon/notes/html/nt/hebrews/hebrews.htm