“If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron?” (Hebrews 7:11, KJV 1900)
There are many jobs in which there is little job satisfaction. This is because the work seems never finished. One such is that of painting long bridges. The painter starts at one end and begins painting. However, when he gets to the other end, he looks back to where he started and sees that the bridge is not perfect for the first part of the bridge has already started to show paint deterioration and rust. So, he goes back to the beginning and starts all over again. This is the way it was for the priesthood under the Levitical order.
The Law established a system of sacrifices officiated by the priests for the sins of the people. When they sinned, they would offer a sacrifice for sin. However, very soon, they would sin again, necessitating the engagement of the process all over again. In addition, every year on the Day of Atonement, the high priest would offer the blood of the sacrifice to atone first for himself and then for the sins of the people. The process of sacrifice needed to be repeated over and over again, year after year. The author of Hebrews is pointing out that this system under the Law could never make one perfect and thus, a new order was necessary. The people kept on sacrificing and the priests kept on doing their work, but never saw the people achieve perfection.
So then, what was the purpose of this system? The sacrificial system of the Law, was there to reveal many truths to the people of Israel and to foreshadow the finished work of Jesus Christ on the cross as the perfecting sacrifice, with Him as both the sacrifice and the eternal great high priest.
Regarding the truths the system was to teach the people of Israel, they were to understand the holiness of God. They were to understand that they could not approach God with the guilt of their sin. He was holy and they were not. The sacrifice demonstrated to them that the penalty of sin was death. Without the shedding of blood there is no remission. They were to understand their hopelessness in trying to keep the Law for righteousness so that they would humbly depend upon God’s infinite mercy. Every time they would make a sacrifice for sin they were to understand that sinners could not stand in God’s presence.
The author here is showing his Jewish audience that another priestly order was essential, because under the Levitical order, no one could ever find perfect atonement forever. This is where Jesus as the eternal great high priest comes in. He took upon Himself the sins of all men and as the spotless Lamb of God, died, shedding His blood for the perfect atonement of all who would trust in him.