A Brief Description Denoting the Intricate Relationship, Comparison, and Connection of the Abrahamic and Mosaic Covenants in Direct Relation to their Application to the Letter of Paul to the Church in Galatia, particularly 3:15-18
“To give a human example, brothers: even with a man-made covenant, no one annuls it or adds to it once it has been ratified. Now 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. This 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. For if the inheritance comes by the law, it no longer comes by promise; but God gave it to Abraham by a promise.”
1) Abrahamic Covenant: Where God promised: 1) To make of Abraham a great nation and bless Abraham and make his name great so that he will be a blessing, to bless those who bless him and curse him who curses him. All peoples on earth will be blessed through Abraham. 2) To give Abraham’s descendants all the promised land. 3) To make Abraham the father of many nations and of many descendants and give “the whole land of Canaan” to his descendants. (See Genesis 12-17) Circumcision is to be the permanent sign of this everlasting covenant with Abraham and his male descendants.
2) Mosaic Covenant: Where God promises to make the Israelites His treasured possession among all people and to make them a kingdom of priests and a holy nation if they follow God’s commandments (Exodus 19-24).
The Relation of the Covenants to Galatians 3:15-18
God made a covenant promise to Abraham and this promise will stand forever. Because God made another covenant promise with His people through Moses at Sinai does not mean the former covenant made to Abraham is void and no longer needed. The two covenants, though different in content and application for the people of God, find their the fulfillment in Jesus. The Abrahamic Covenant is fulfilled in Jesus, because He is the one Descendant who’ll bless all the families of the earth (Genesis 12:3). The Mosaic Covenant is fulfilled in Jesus, because He is only One who can keep the Law of God, which points out our need for Christ (Galatians 3:24) and reveals the righteousness provided to us through His Law-keeping (2 Corinthians 5:21).
Bottom line? When God interacts with His people He does so through covenant. All of the covenants (Covenant of Works, Covenant of Grace, Noahic Covenant, Abrahamic Covenant, Mosaic Covenant, Davidic Covenant, and the New Covenant) contain requirements of the people of God, and more so exist to point to Jesus, find their fulfillment in Jesus, and reveal glorious things about Jesus.