Sometimes, we forget that the new covenant “is superior to the old one, and it is founded on better promises. For if there had been nothing wrong with that first covenant, no place would have been sought for another.” (Hebrews 8:6-7)
“If perfection could have been attained through the Levitical priesthood (for on the basis of it the law was given to the people), why was there still need for another priest to come — one in the order of Melchizedek, not in the order of Aaron? For when there is a change of the priesthood, there must also be a change of the law.” (Hebrews 7:11-12)
The law was changed and necessarily.
“The time is coming, declared the Lord, when I will make a new covenant with the house of Israel and with the house of Judah. It will not be like the covenant I made with their forefathers… This is the covenant I will make… I will put My laws in their minds and write them on their hearts. I will be their God, and they will be My people. No longer will a man teach his neighbor, or a man his brother, saying, ‘Know the Lord,’ because they will all know Me, from the least of them to the greatest. For I will forgive their wickedness and will remember their sins no more.” (Hebrews 8: 8,9,10,11-12)
Notice the “blood of Christ, who through the eternal Spirit offered Himself unblemished to God, cleanses our consciences from acts that lead to death, so that we may serve the living God.” (Hebrews 9:14) Christ came to be the “mediator of a new covenant” because no “external regulation” was able “to clear the conscience of the worshiper.” (Hebrews 9:15; 9:9) The old covenant of “external regulations” is “obsolete, and what is obsolete and aging will soon disappear.” (Hebrews 8:13)
In order to serve the living God, our consciences must be clear. Christ “died as a ransom to set [us] free from the sins committed under the first covenant.” (Hebrews 9:15) “He has appeared once for all at the end of the ages to do away with sin by the sacrifice of Himself.” (Hebrews 9:26) “He will appear a second time, not to bear sin, but to bring salvation to those who are waiting for Him.” (Hebrews 9:28)