11Therefore, if perfection were through the Levitical priesthood (for under it the people received the law), what further need was there that another priest should rise according to the order of Melchizedek, and not be called according to the order of Aaron? 12For the priesthood being changed, of necessity there is also a change of the law. (Heb. 7:11-12)
The book of Hebrews is hard to grasp for many people. However, it is actually not that hard to understand, once we know what the main theme of Hebrews is and in what context it was written.
The book of Hebrews was written to Jewish Christians who, because of persecution, were tempted to compromise with their faith in order to once again be accepted and included in the Jewish society. The temptation was to reject their faith in Jesus, the mediator of the New Covenant, and to, instead of trusting in Jesus and His grace alone for their salvation, return to the law of Moses and the Old Covenant. The writer of Hebrews (we do not know for sure whether it was Paul or someone else) is, like a lawyer before the court, vehemently defending the New Covenant and salvation by grace through faith in Jesus Christ, as opposed to salvation by the law, i.e. our own performance.
The book of Hebrews is full of contrasts. Again, and again, the author points out how much better the New Covenant is, compared to the Old.
Jesus is greater than the Old Testament Prophets
The author starts by saying that God used to speak through his prophets, but now He has spoken through his Son, who is the prefect representation and image of God. He is basically saying, the prophets of the Old Covenant were great, but Jesus and the New Covenant is greater (Heb. 1:1-3).
Jesus is greater than the angels and Moses
He goes on to say that the law of Moses was given to man by angels, but Jesus, the mediator of the New Covenant, is greater than all the angels (Heb. 1:4-2:18). Moses, who received the law, was a trusted servant of God, but Jesus is not only God’s servant, but God’s son! Therefore, Jesus (the Son) and the New Covenant is greater than Moses (the servant) and the Old Covenant (Heb. 3:1-6).
Jesus represents a greater priesthood
After that he moves on to talk about the priesthood of the Old versus the New Covenant. The Levitical priesthood of the Old Covenant had shortcomings, because the priests did not only have to offer repeated gifts and sacrifices for the sins of the people, but also for themselves. Jesus, on the other hand, is a High Priest from a greater linage, after the order of Melchizedek. Jesus, being God’s Son, was without sin and therefore did not have to offer sacrifices on His own behalf. By the sacrifice of Himself on the cross, Jesus once for all took away sins the sins of the world, and therefore animal sacrifices are no longer necessary (Heb. 4:14-10:22).
Since Jesus introduced a new priesthood, after the order of Melchizedek, He also introduced a new law; a New and better Covenant, based on God’s grace, which has replaced the law of Moses and the Old Covenant (Heb. 7:11-10:9).
How are we to understand the book of Hebrews? It is simply a book written to show us that the New Covenant is greater than the Old Covenant, that the Old Covenant has expired, and that we are to stick with the New Covenant only!
Start reading the book of Hebrews with this knowledge and you will understand it, and the New Covenant, like never before.