An important characteristic of God when it comes to salvation is what is referred to as his immutability. It says in Hebrews 6:17-18, “Thus God, determining to show more abundantly to the heirs of promise the immutability of His counsel, confirmed it by an oath, that by two immutable things, in which it is impossible for God to lie, we might have strong consolation, who have fled for refuge to lay hold of the hope set before us.” The Greek word translated immutability, amethatetos (am-et-ath’-et-os) means unchangeable (G276). Amethatetos has to do with decision making and at a deeper level deals with loyalty to a particular person or viewpoint. The immutability of God’s counsel refers specifically to his will, the things that he intends to accomplish and uses his power to control.
The Old Covenant which dealt with Abraham’s descendants being brought into an eternal relationship with God was the primary reason Jesus came to Earth and died for the sins of the world, but even before Jesus was born, God said that he was going to establish a New Covenant that would finish the work of salvation that began with Abraham (Jeremiah 31:33). Whereas the Old Covenant was a conditional covenant, meaning there were conditions that had to be met in order for it to be fulfilled, the New Covenant was enacted by God as “an unconditional divine promise to unfaithful Israel to forgive her sins and establish His relationship with her on a new basis by writing His law ‘in their hearts’ — a covenant of pure grace” (Major Covenants in the Old Testament, p. 16).
The writer of the book of Hebrews explained God’s New Covenant in the context of the Mosaic Law. The Jews had been living according to God’s commandments for hundreds of years, but were told, “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? For the priesthood being changed, there is made of necessity a change of the law also” (Hebrews 7:11-12). God’s standard of perfection was never meant to be attained by humans. The Mosaic law had to do with physical requirements that could extend one’s physical life; keeping the commandments was not expected to result in eternal life (Hebrews 7:16).
The writer of Hebrews determined that the Mosaic Law merely paved the way for something better that would accomplish what God originally intended, the restoration of his relationship with mankind (Hebrews 7:18-19). He said, “by so much more Jesus has become a surety of a better covenant. Also there were many priests, because they were prevented by death from continuing. But He, because He continues forever, has an unchangeable priesthood” (Hebrews 7:22-24, NKJV). Basically, what this means is that Jesus has made it possible for the God’s work of salvation to continue uninterrupted. It is an eternal ministry that will never come to an end. The reason this is important is because sin can only be eliminated if it is permanently deleted from God’s record. The temporary covering that was originally accomplished through the sacrifice of animals was replaced with a perpetual, unchangeable atonement by the blood of Jesus Christ (Hebrews 7:27).