The whole Bible is a historically redemptive outworking of the covenant of grace. The sovereign and holy Creator of the the universe has mercifully condescended to save sinners from the just penalty of their sins. He has done that by covenant. He has made an oath and sworn by Himself, that He will be a God unto those who will rest upon His work and word to redeem them.
We first saw the promise of this covenant mercy in Genesis 3:15. Immediately after the fall, God comes to an undone Adam and Eve and pursues them in their sin in order to save them from their sin. They have broken the covenant of works. They have eaten of the forbidden fruit and they are in the biggest mess possible. They are without hope if left to themselves.
God deals with their sin. Most certainly things have changed for Adam and Eve. They will die. They will labor in tiresome ways. They will hurt. They will know sorrow. Yet, they will find hope in the promise of God's redemptive mercy. Satan seeks to steal, kill, and destroy them. He has stolen much from them due to their own rebellion but He is a defeated enemy. To the crafty serpent God declares: "And I will put enmity between you and the woman, and between your seed and her seed; He shall crush you on the head and you shall bruise Him on the heel." (Gen 3:15).
Here is the first proclamation of the gospel. God will send Christ, the seed of the woman (note a prophecy of the incarnation and virgin birth) to crush the head of mankind's great enemy. "No sooner was the wound given than the remedy was provided and revealed." (Matthew Henry).
Throughout the pages of the Old Testament we continually learn a little bit more about this covenant of grace. In Noah we see of our need to flee into Christ the ark. In Abraham we learn that we are justified by faith and not by works and we see the sign of the covenant instituted and given to believers and their household. In Moses we see learn of the righteous requirements of the Law of God and that points us to the One pefect keeper of the Law of God and we are given the second sacrament, the sacrament of communion as it is portrayed in the Passover. In Moses we see Christ as both our Prophet and our Priest. In David we see Him as our King. On and on it goes. God throughout His word has made promises to believers, their children and their whole household.
So now we come to this "new covenant." Yet even in it the language is the same as the old. He will still be their God and they will still be His people. The new part is the fulfilling of the gospel. In Christ all of the old types have been accomplished. The shadows are now light. The veil is now torn. The promise is now reality. The covenant is new and improved for Christ has come and done. When He cried "it is finished" it truly was!
In the Old Covenant God wrote His law TO them now He writes it IN them. Truly this is a better place to be. Yet, it is relationally the same place. "I will be their God and they shall be My people." Here is the old promise still in effect.
"God promises to take them into a near and very honorable relation to Himself. He will be to them a God. Nothing more can be said in a thousand volumes than is compreheneded in these few words, "I will be their God and they shall be My people."
Christ has accomplished much for us. Under the Old Covenant they looked forward to what the Messiah would accomplish and they lived by faith in what was to come. Now we look back to what He has done. We are most assuredly a priviliged people to live on this side of the cross. We have the whole counsel of God before us and the freedom and ability to read it whenever we want.
Is He your God and are you His people? If not, flee to Christ, the promised Lamb who was slain on Calvary's cross to save sinners.