Here's the initial promise to Abraham:
Genesis 12
1: Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father's house, unto a land that I will shew thee:
2: And I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing:
3: And I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed.
Immediately, we can see that there are two groups involved. A "great nation" and "the families (or nations) of the earth".
Fast forward a little.
Genesis 15
4: And, behold, the word of the LORD came unto him, saying, This shall not be thine heir; but he that shall come forth out of thine own bowels shall be thine heir.
5: And he brought him forth abroad, and said, Look now toward heaven, and tell the stars, if thou be able to number them: and he said unto him, So shall thy seed be.
6: And he believed in the LORD; and he counted it to him for righteousness.
So, Abraham, a heathen, yet uncircumcised, was counted as righteous by faith alone. No action was required in believing God's promise.
Moving ahead, God changes his name from Abram to Abraham and...
Genesis 17
10: This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.
11: And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you.
12: And he that is eight days old shall be circumcised among you, every man child in your generations, he that is born in the house, or bought with money of any stranger, which is not of thy seed.
14: And the uncircumcised man child whose flesh of his foreskin is not circumcised, that soul shall be cut off from his people; he hath broken my covenant.
The covenant of circumcision is given to Abraham, and an action IS required to remain in this covenant.
So, within the umbrella of the Abrahamic covenant, Gen 12:1-3, God is now beginning to set apart the "great nation" within that covenant.
From Gen 17 forward, it's all about the circumcision. It's all about getting that "great nation" through whom the nations of the earth would be blessed.
Well, the Messiah comes to the circumcision. The majority reject him, he's crucified, buried, risen, and ascended. Israel continues to reject the ministry of the Holy Spirit in early Acts, Israel is fallen.
But, God raises up another apostle with a message that was hidden in the scriptures concerning Gentiles, the uncircumcision.
Gal 3
5: He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith?
6: Even as Abraham believed God, and it was accounted to him for righteousness.
7: Know ye therefore that they which are of faith, the same are the children of Abraham.
8: And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.
9: So then they which be of faith are blessed with faithful Abraham.
So, instead of blessing the nations of the world through the rise of that "great nation", they are blessed through the fall of that "great nation"...and, he can do it by their faith alone.
During Acts, you have two groups. Both are the children of Abraham, and both fall under the umbrella of the Abrahamic covenant. One group, a nation, are children of Abraham (in circumcision). The other group, a Body, are children of Abraham (in uncircumcision). The covenant of circumcision requires action, works. No action is required of the uncircumcision.
You can follow these two groups through the book of Acts. You can see the circumcision being diminished, you can see the uncircumcision growing.
The two groups are clearly seen here,
Gal 2
7: But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
8: (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles: )
9: And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
In Galatians, Paul contrasts the two covenants which spawn these two groups. He contrasts the Abrahamic covenant with the Mosaic (the circumcision). The promise is unto both, the Jerusalem above which is free, is the mother of them all.
Hope this helps...
