We see this in the Old Testament when Moses wrote in Numbers 23:9, For from the top of the rocks I see him, and from the hills I behold him: lo, the people shall dwell alone, and shall not be reckoned among the nations. We see it again when is further wrote in Deuteronomy 7:6, 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.
The Bible also says that it would be through the nation of Israel specifically that God would bring salvation to the world. Isaiah 46:13 says, I bring near my righteousness; it shall not be far off, and my salvation shall not tarry: and I will place salvation in Zion for Israel my glory. Also, Zechariah 8:19-23 says, Thus saith the LORD of hosts; The fast of the fourth month, and the fast of the fifth, and the fast of the seventh, and the fast of the tenth, shall be to the house of Judah joy and gladness, and cheerful feasts; therefore love the truth and peace. Thus saith the LORD of hosts; It shall yet come to pass, that there shall come people, and the inhabitants of many cities: And the inhabitants of one city shall go to another, saying, Let us go speedily to pray before the LORD, and to seek the LORD of hosts: I will go also. Yea, many people and strong nations shall come to seek the LORD of hosts in Jerusalem, and to pray before the LORD. Thus saith the LORD of hosts; 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.
The Psalmist also prophecies that He hath remembered his mercy and his truth toward the house of Israel: all the ends of the earth have seen the salvation of our God in Psalms 98:3, i.e., salvation was first going to start with the Jews and then the ends of the earth. It was not God's plan that every Gentile become a member of Israel, but instead that they receive salvation from the God of Israel. There is a difference.
Also, the Psalmist wrote in Psalms 72:1-20, Give the king thy judgments, O God, and thy righteousness unto the king's son. He shall judge thy people with righteousness, and thy poor with judgment. The mountains shall bring peace to the people, and the little hills, by righteousness. He shall judge the poor of the people, he shall save the children of the needy, and shall break in pieces the oppressor. They shall fear thee as long as the sun and moon endure, throughout all generations. He shall come down like rain upon the mown grass: as showers that water the earth. In his days shall the righteous flourish; and abundance of peace so long as the moon endureth. He shall have dominion also from sea to sea, and from the river unto the ends of the earth. They that dwell in the wilderness shall bow before him; and his enemies shall lick the dust. The kings of Tarshish and of the isles shall bring presents: the kings of Sheba and Seba shall offer gifts. Yea, all kings shall fall down before him: all nations shall serve him. For he shall deliver the needy when he crieth; the poor also, and him that hath no helper. He shall spare the poor and needy, and shall save the souls of the needy. He shall redeem their soul from deceit and violence: and precious shall their blood be in his sight. And he shall live, and to him shall be given of the gold of Sheba: prayer also shall be made for him continually; and daily shall he be praised. There shall be an handful of corn in the earth upon the top of the mountains; the fruit thereof shall shake like Lebanon: and they of the city shall flourish like grass of the earth. His name shall endure for ever: his name shall be continued as long as the sun: and men shall be blessed in him: all nations shall call him blessed. Blessed be the LORD God, the God of Israel, who only doeth wondrous things. And blessed be his glorious name for ever: and let the whole earth be filled with his glory; Amen, and Amen. The prayers of David the son of Jesse are ended.
Plan A was that after Israel's national salvation was offered at Pentecost, the nation would be ministers and priests of the Lord taking salvation to the Gentiles as foretold in Isaiah 61:1-6, The Spirit of the Lord GOD is upon me; because the LORD hath anointed me to preach good tidings unto the meek; he hath sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to them that are bound; To proclaim the acceptable year of the LORD, and the day of vengeance of our God; to comfort all that mourn; To appoint unto them that mourn in Zion, to give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness; that they might be called trees of righteousness, the planting of the LORD, that he might be glorified. And they shall build the old wastes, they shall raise up the former desolations, and they shall repair the waste cities, the desolations of many generations. And strangers shall stand and feed your flocks, and the sons of the alien shall be your plowmen and your vinedressers. But ye shall be named the Priests of the LORD: men shall call you the Ministers of our God: ye shall eat the riches of the Gentiles, and in their glory shall ye boast yourselves.
In conclusion, to say that we have become Israel denies the very reason that God separated them from among the nations. So, the second thing they must do to see the church as Israel is to reject the significance of God's separation of Israel from the Gentiles.