There is a connection between the Covenant of Abraham and the Covenant of Moses' Law that is tenuous and temporary. Paul called the Abrahamic Covenant a "promise," and he called the Law "temporary." He saw Christ as the eternal fulfillment of that promise, leading to the fulfillment of the Abrahamic Covenant. The Law, initially connected to that Covenant, was a temporary fill-in.
Rom 4.13 It was not through the law that Abraham and his offspring received the promise that he would be heir of the world, but through the righteousness that comes by faith. 14 For if those who depend on the law are heirs, faith means nothing and the promise is worthless, 15 because the law brings wrath. And where there is no law there is no transgression.
Gal 3.14 He redeemed us in order that the blessing given to Abraham might come to the Gentiles through Christ Jesus, so that by faith we might receive the promise of the Spirit. 15 Brothers and sisters, let me take an example from everyday life. Just as no one can set aside or add to a human covenant that has been duly established, so it is in this case. 16 The promises were spoken to Abraham and to his seed. Scripture does not say “and to seeds,” meaning many people, but “and to your seed,” meaning one person, who is Christ. 17 What I mean is this: The law, introduced 430 years later, does not set aside the covenant previously established by God and thus do away with the promise. 18 For if the inheritance depends on the law, then it no longer depends on the promise; but God in his grace gave it to Abraham through a promise.
Abraham was promised the salvation of Israel and of many nations of faith. But this covenant was made with Abraham, as well as with Christ, on the basis of circumcision, and it was made with Israel on the basis of the Law of Moses.
Christ did not immediately come to bring final redemption for those under the Law, who remained hindered from access to the Tree of Life. And this was the purpose of the Law, to confirm that access to the Tree of Life was hindered by the guilt of human sin, and to show that the promises of God could not be fulfilled until guilt was completely and finally dealt with.
Gen 3. 23 So the Lord God banished him from the Garden of Eden to work the ground from which he had been taken. 24 After he drove the man out, he placed on the east side of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life.
But God provided hope, through the Messiah, a descendant of Eve, of a means back to the Tree of Life.
Gen 3.14 14 So the Lord God said to the serpent,... 15 And I will put enmity between you and the woman, and between your offspring and hers; he will crush your head, and you will strike his heel.”
God's plan of redemption of humanity after the Fall continued with Abraham, and this is what Paul referred to as the "promise"...
Gen 17.1 When Abram was ninety-nine years old, the Lord appeared to him and said, “I am God Almighty; walk before me faithfully and be blameless. 2 Then I will make my covenant between me and you and will greatly increase your numbers.”
3 Abram fell facedown, and God said to him, 4 “As for me, this is my covenant with you: You will be the father of many nations. 5 No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. 6 I will make you very fruitful; I will make nations of you, and kings will come from you. 7 I will establish my covenant as an everlasting covenant between me and you and your descendants after you for the generations to come, to be your God and the God of your descendants after you. 8 The whole land of Canaan, where you now reside as a foreigner, I will give as an everlasting possession to you and your descendants after you; and I will be their God.”
9 Then God said to Abraham, “As for you, you must keep my covenant, you and your descendants after you for the generations to come. 10 This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised."
The problem was, the Law was given to restrict access to the Tree of Life, while at the same time providing a basis for a relationship between God and Israel. Since the Law restricted access to the Tree of Life, its practice was strictly temporary, until Christ could come and establish both a relationship with God and access to the Tree of Life.
The Law therefore had to be detached, along with circumcision, from the covenant God made with Abraham and with Christ, Abraham's seed. As long as the Law was connected to this covenant, the promise of international salvation could not take place. Relationship between God and Israel would only be temporary.
As I said, the Law established a relationship between God and Israel, but it was a tenuous relationship, conditioned on replacing this temporary enablement of the Law with something permanent. Therefore, the Law had to be detached as a limiting element of this covenant, to enable man to have access to Christ, the source of eternal life.
In what way did the Law inform Israel of the limitations placed on their relationship with God? It set up barriers, including veils and walls, between God and Israel. A priesthood separated God from the people in some respects. And all were unable to approach God without carrying out certain rituals of purification.
Heb 9.6 When everything had been arranged like this, the priests entered regularly into the outer room to carry on their ministry. 7 But only the high priest entered the inner room, and that only once a year, and never without blood, which he offered for himself and for the sins the people had committed in ignorance. 8 The Holy Spirit was showing by this that the way into the Most Holy Place had not yet been disclosed as long as the first tabernacle was still functioning. 9 This is an illustration for the present time, indicating that the gifts and sacrifices being offered were not able to clear the conscience of the worshiper. 10 They are only a matter of food and drink and various ceremonial washings—external regulations applying until the time of the new order.
Good works were required of men by God, while at the same time the Law exposed human sin as preventing them from accessing eternal life. As long as the Law was in effect and connected to Abraham's covenant, eternal life could not be had, and unfettered access to God's salvation could not be had.
Good works, though they be good, would be mixed with bad works, and denial of access to the Tree of Life would continue to be enforced by angels. The best of the saints would be denied, despite their faith in God, the ultimate fulfillment of God's promises, at least until Christ could come and complete their hope.
Gal 2.16 know that a person is not justified by the works of the law, but by faith in Jesus Christ. So we, too, have put our faith in Christ Jesus that we may be justified by faith in Christ and not by the works of the law, because by the works of the law no one will be justified.
The limitations of the Law are removed when it is recognized that Christ provided final purification for Israel and for the world. Faith in Christ allows us to follow him, the source of eternal life. And following him enables us to live like him and have our flaws atoned for in the process.
Christ alone is the way to the Tree of Life, and the only way to have a blessed and an eternal relationship with God. The Law was temporary, and had to be stripped from the promises contained in Abraham's Covenant.
When Christ died on the cross, he gave up any need for Israel to participate, under the Law, in self-atonement. All the guilt of human sin died with Christ on behalf of those who choose to put their faith in him and to follow him.
Living by his Spirit enables us to both be like him and to be atoned by him. It is the fulfillment of God's promise of redemption. It is the only way back to the Tree of Life. Any return to the Law of Moses condemns us forever.