In the NT Jesus introduces us to the concept of 2 Israels (Mat 19.28).
This is as a result of his Born Again teaching (John 3).
Hence, Paul later distinguishes between the Born-again, immortal Israel of God, Gal 6.16) and the mortal national, ethnic Israel of the flesh (1Cor 10:18a).
So that now Jewish-Christians along with Gentile-Christians are called the true circumcision (Phil 3.13) because they have believed, repented, i.e., have been born again.
This Born Again Israel now stands in sharp contrast to present-day unbelieving, therefore unrepentant, not Born Again nation of Israel.
Including both non-religious and religious Jew who remains bound to the physical, literal circumcision of the flesh (Gal 6.13).
This explains why Paul devotes most of his letters to matters related to the OC Law of Moses as opposed to the NC Law of Christ.
In other words, the Law of Moses is represented by the circumcision of the flesh and not of the spirit, as we shall see.
Circumcision: gateway to Torah-keeping
First and foremost circumcision of the flesh was the sign of the Abrahamic covenant, i.e., God's promise to Abram that he would inherit the land and as a result, become the father all the nations of the world: Gen 17:13-14; Ex 12.48.
Hence, God changes Abram's name to Abraham, aka the father of many nations.
Later, under the Mosaic covenant, circumcision becomes the gateway for Torah-keeping (Acts 15.5).
Hence, the various OT warnings re: the uncircumcised not being able to enter into the promises of the KOG: Isa 52.1; Ezek 44.9.
The point being that if you were not circumcised you would be cut off from the land promise, i.e., no good news for you!
Replacement Theology
As a result of the NT revelation re: the 2 Israels concept is sometimes seen through the prism of what's known as replacement theology.
Now there is a right and a wrong way to talk about the concept.
Wrongly defined as the Church fully and permanently replacing national-ethnic Israel of the flesh.
Rightly defined as the new olive tree of God, the international, Born Again Israel of God if you will, made up of both Jew/Gentile: Romans 11.
This means there will be a saved remnant of ethnic/national “Israel of the flesh,” as Jesus says in Mat 19.28.
BTW just like there will be survivors from every other nation in the world, Ezek 36.36; Zech 14.16; cp. Isa 19.20f.
OT vs NT Israel
So when reading the OT we must carefully distinguish between prophecies pertaining to national/ethnic Israel and the spiritual, born again Israel of God (aka the Church).
National/ethnic Israel of the flesh
For example, Paul in Rom 9:
v. 26 applies Hosea 1:10;
v. 28 applies Isa 10:22–23;
v. 29 applies Isa 1:9.
Romans 11.
v. 8 applies Deut. 29:4; Isa 29:10 to national Israel.
v. 10 applies Psalm 69:22–23;
v 15: “the dead coming back to life" in the Valley of dry bones in Ezek. 37, not a reference to the resurrection of the dead!
v. 27 applies Isaiah 27:9; 59:20–21.
Other applications:
Isa. 65.17-25 the mortal nation of Israel in the KOG;
Ezekiel 36f., re: Israel and reestablishment of modified Torah(?) and the Millennium Temple.
National/ethnic Israel of the flesh becomes part of the rest of the remnant nations in the KOG:
Isa 19.18f. triple alliance with former enemy-states like Egypt, Assyria; aka the New United KOG Nations!
Born Again, spiritual Israel
Again Paul in Rom 9:
vv. 6-7 applies Gen 21.12;
v. 9 applies Gen 18:14;
vv. 12-13 applies Gen 25:23; Mal 1:2–3;
Other applications:
OT “the elect/saints” language applied Matt 24.22-31.
Born Again Israel of God, 1 Pet. 2:9-10:
“You (the church) are a chosen people (quoting Isa. 43:20), a royal priesthood, a holy nation (quoting Exodus 19:6), a people belonging to God (Deut. 7:6), that you may declare the praises of Him who called you out of darkness into his wonderful light (quoting Isaiah 43:21). Once you were not a people of God, once you had not received mercy, but now you have received mercy” (Hosea 2:23).
What the Future holds.
The Born Again Israel of God/the Church will govern the remnant nations at the paligenesia [Age to come/KOG on earth] including national, ethnic Israel of the flesh: Mathew 19.28!
