15To give a human example, brothers: even with a man-made covenant, no one annuls it or adds to it once it has been ratified. 16Now the promises were made to Abraham and to his offspring. It does not say, “And to offsprings,” referring to many, but referring to one, “And to your offspring,” who is Christ. 17This is what I mean: the law, which came 430 years afterward, does not annul a covenant previously ratified by God, so as to make the promise void. 18For if the inheritance comes by the law, it no longer comes by promise; but God gave it to Abraham by a promise.
Old Testament covenants were permanent. They were not simply laid in place until something else came along. Covenants were not easily amended and they were certainly not annulled once they had been confirmed or applied. When one party made a covenant with another, the covenant was confirmed by an action. In the covenant between Johnathan and David, Johnathan confirms the covenant by giving David his armor and robe (1 Sam 18:3-4). The Elders of Hebron confirmed their covenant with David by anointing him with oil (2 Sam 5:3). When God makes His covenant with Noah, he hangs floods the earth to confirm it and then hangs His bow in the sky (Gen. 6 and Gen. 9:8-17)! Further, the nature of the covenant was secured by the character of the strongest party involve. Pause for a moment and consider the implications of God’s character on the security of the covenants He has made. There is no greater name by which a promise can be secure. The God who holds all things together has covenanted with you. The God in whom we live and move and have our being has come down from Heaven and covenanted with people. There is no greater character by which your promises are secure.
The specific covenant Paul references here in this passage is found in Genesis 12. Abram is called by God to go to a new land that God will show him. He is told that God will give his offspring that land and Abram builds an altar in worship to God for the promise (Gen 12:4-7). Three chapters later, God ratifies his covenant with Abram through one of the most beautiful symbols of all Scripture. He has Abram kill and cut in half multiple animals and then line them up with a path through the middle of the split animals. Then Abram has a vision/dream of a torch and smoking pot going through the two halves of the animals.
In the vision, God is represented by the torch and the smoking pot. Abram is watching from the side. In essence, God establishes that He alone is the keeper of the covenant. In this act, God declares if either party breaks the covenant, may He be torn in two like these animals. And so, when humanity breaks the covenant with God, Jesus is rent in two in order to pay the price of the covenant! The ratification of the covenant of Abram is fulfilled and completed in Jesus. God maintains the covenant with those who have faith by dying for us. Oh What a great God who holds us together and lays down His life for our salvation!
So this is the covenant that Paul references in Galatians 3. This is separate from the covenant of Circumcision given to the Jewish people in Genesis 17. That covenant is a covenant based on the behavior of the Jewish people. It requires adherence to the law of God. God is still gracious and offers mercy through the law, but there is no righteousness gained through law. The Law serves only to show man’s sin. The only way to be righteous is to trust in Christ, who tore Himself in two for your salvation! Repent from your sin and confess to Christ that you need Him to save you! The blessing of Abraham is secure for those who have faith in the work of Jesus Christ – The Offspring! He owns the land of salvation! So, when we trust in Christ, we become “fellow heirs” with Jesus and receive the promise of salvation and presence with God (Eph. 3:6; c.f. Romans 8:16-17).