Darby's type of dividing was 2P2P which does not exist in the Bible.
First people of God and First Program
First we see that in the OT the children of Israel were "above all people that are upon the face of the earth:
"For thou art an holy people unto the LORD thy God: the LORD thy God hath chosen thee to be a special people unto himself, above all people that are upon the face of the earth" (Deut.7:6).
According to the OT prophecies the Gentiles will hasten to Israel because they will see that the LORD has endowed her with splendor:
"Surely you will summon nations you know not, and nations that do not know you will hasten to you, because of the Lord your God, the Holy One of Israel, for he has endowed you with splendor" (Isa.55:3).
According to the OT prophecies the houses of Israel and Judah will be a blessing and Gentiles will come to the knowledge of the LORD through the agency of the Jews:
"And it shall come to pass, that as ye were a curse among the heathen, O house of Judah, and house of Israel; so will I save you, and ye shall be a blessing...In those days it shall come to pass, that ten men shall take hold out of all languages of the nations, even shall take hold of the skirt of him that is a Jew, saying, We will go with you: for we have heard that God is with you" (Zech.8:13,23).
Second People of God and Second Program
Today there are no special people of God except those in the New Man, the Body of Christ, where there is neither Greek nor Jew:
"And have put on the new man, which is renewed in knowledge after the image of him that created him: Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all" (Col.3:10-11).
We can also see that it is through Israel's fall that salvation has come to the Gentiles:
"I say then, Have they stumbled that they should fall? God forbid: but rather through their fall salvation is come unto the Gentiles, for to provoke them to jealousy. Now if the fall of them be the riches of the world, and the diminishing of them the riches of the Gentiles; how much more their fulness?" (Ro.11:11-12).
Today it is those in the Body of Christ who have been given the "ministry of reconciliation" to preach the "word of reconciliation":
"And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation; To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation. Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God. For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him" (2 Cor.5:18-21).
This proves conclusively that during history there has been two people of God as well as two programs.