No, that's not true. Do you know what the "Diaspora" is?
It all starts with one person. God chooses one person, and it begins there. There are many "one person" examples in Scripture. Noah, Abraham, Isaac, Jacob, Moses, Samson, Boaz, etc. Some of the major doctrines we have in true, biblical Christendom was the result of "one person" whom God would choose and send. There are hundreds of examples in Scripture and there are hundreds of examples after Scripture. People like Augustine, Edwaards, Hodge, Wilkerson, Cruz, Arguinzoni.
God has shown us He saves by covenant. Abraham, Isaac, Jacob, and others who are born from the seed of Abraham are in covenant for a reason as we see God's purpose every succeeding generation of Hebrews who are born, instructed as heir of covenant until we come to the three million Hebrews delivered out of Egyptian bondage to be taken into the desert and God making a covenant with them called the Mosaic Covenant called the Law of Moses and His God. A New Covenant is prophesied by one of Israel's prophets whom God sent to the southern kingdom tribe of Judah (and Benjamin) and in this covenant God promises to forgive the people of the ten northern kingdom tribes of the House of Israel; and the two southern kingdom tribes of the House of Judah. The promise and prophecy is found in Jeremiah 31:31-34. As you can see this covenant comes with forgiveness of Israel's sin but contains no mechanism of atonement and propitiation as the Mosaic Covenant has. The only conclusion is that Jesus Christ came in fulfillment of promises and prophecies in Scripture to fulfill the Ceremonial Law of the Law of Moses and in substitute for the animal that the high priest slain to atone for the sins of the children of Israel the only conclusion is that to get to the New Covenant God made with the Hebrew people that Christ would be sent and fulfill the elements of atonement and died for the children of Israel the same as the animal was slain to atone for the sins of the children of Israel even if it was only a one-year, perpetual, ritual that God used for a time as He prepared His Christ for the children of Israel. The New Covenant is only the Mosaic Covenant fulfilled by Christ and it is this sacrifice of the lamb of God that God used to inaugurate the New Covenant with both the House of Israel and the House of Judah.
Promises made, promises kept.
You have ignored a ton of scripture from the New Testament and also the Old Testament
Romans 3:21–26 (LEB) — 21
But now, apart from the law, the righteousness of God has been revealed, being testified about by the law and the prophets—22
that is, the righteousness of God through faith in Jesus Christ to all who believe. For there is no distinction, 23 for all have sinned and fall short of the glory of God, 24 being justified as a gift by his grace, through the redemption which is in Christ Jesus, 25 whom God made publicly available as the mercy seat through faith in his blood, for a demonstration of his righteousness,
because of the passing over of previously committed sins, 26 in the forbearance of God, for the demonstration of his righteousness in the present time, so that he should be just and the one who justifies the person by faith in Jesus.
That would include gentiles.
And so Paul informs
Romans 3:27–31 (LEB) — 27 Therefore, where is boasting? It has been excluded.
By what kind of law? Of works? No, but by a law of faith. 28 For we consider a person to be justified by faith apart from the works of the law. 29 Or is God the God of the Jews only?
Is he not also the God of the Gentiles? Yes, also of the Gentiles, 30
since God is one, who will justify those who are circumcised by faith and those who are uncircumcised through faith.
Gal 1:16to reveal his Son in me in order that I would
proclaim the gospel about him among the Gentiles, immediately I did not consult with flesh and blood,
He did so in fact do
Gal 2:2Now I went up there because of a revelation and
laid out to them the gospel that I preach among the Gentiles, but in private to the influential people, lest somehow I was running, or had run, in vain.
Gal 2:8(for the one who was at work through Peter for his apostleship to the circumcision was at work also through me
for the Gentiles),
And His work was approved of by apostles
Gal 2:9and when James and Cephas and John—those thought to be pillars—
acknowledged the grace given to me, they gave to me and Barnabas the right hand of fellowship, in order that we should go to the Gentiles and they to the circumcision.
He was also given help to continue his work with the Gentiles
Gal 2:12For before certain people came from James, he used to eat with the
Gentiles, but when they came, he withdrew and separated himself, because he was afraid of those who were of the circumcision,
While just as you do, some Jews denied the Gentile fellowship
Gal 2:14But when I saw that they were not being straightforward with the truth of the gospel, I said to Cephas in the presence of them all, “If you, although you are a Jew, live like a
Gentile and not like a Jew, how can you try to compel the
Gentiles to live like Jews?”
Paul however noted you both are not being straightforward with the truth of the gospel
Gal 3:8And the scripture, foreseeing that God would justify the
Gentiles by faith,
proclaimed the good news in advance to Abraham: “In you all the nations will be blessed.”
Quoting scripture as was given to Abraham
Genesis 12:3 (LEB) — 3 And I will bless those who bless you, and those who curse you I will curse.
And all families of the earth will be blessed in you.”
Gal 3:14in order that the blessing of Abraham might come to the Gentiles in Christ Jesus, so that we might receive the promise of the Spirit through faith.
Genesis 22:18
All the nations of the earth will be blessed through your offspring, because you have listened to my voice.”
Genesis 26:4
And I will multiply your descendants like the stars of heaven, and I will give to your descendants all these lands. And all nations of the earth will be blessed through your offspring,
Genesis 28:14
Your descendants shall be like the dust of the earth, and you will spread out to the west, and to the east, and to the north and to the south. And all the families of the earth will be blessed through you and through your descendants.
In order that the blessing of Abraham might come to the
Gentiles
BTW if you are going to read Galatians, read this
Gal 3:8And the scripture, foreseeing that God would justify the Gentiles by faith, proclaimed the good news in advance to Abraham: “In you all the nations will be blessed.”
Gal 3:14in order that
the blessing of Abraham might come to the Gentiles in Christ Jesus
, so that we might receive the promise of the Spirit through faith.
Gal 3:28There is neither Jew nor Greek, there is neither slave nor free, there is neither male and female, for you are all one in Christ Jesus.
Gal 3:13Christ redeemed us from the curse of the law by becoming a curse for us, because it is written, “Cursed is everyone who hangs on a tree,”
Gal 3:7then understand
that the ones who have faith, these are sons of Abraham.
Gal 3:9So then,
the ones who have faith are blessed together with Abraham who believed.
Galatians 3:6–14 (LEB) — 6 Just as Abraham believed God, and it was credited to him for righteousness, 7 then understand that
the ones who have faith, these are sons of Abraham. 8 And
the scripture, foreseeing that God would justify the Gentiles by faith, proclaimed the good news in advance to Abraham: “In you all the nations will be blessed.” 9 So then, the ones who have faith are blessed together with Abraham who believed. 10 For as many as are of the works of the law are under a curse, for it is written, “Cursed is everyone who does not abide by all the things that are written in the book of the law to do them.” 11
Now it is clear that no one is justified in the sight of God by the law, because “the one who is righteous will live by faith.” 12 But the law is not from faith, but “the one who does these things will live by them.” 13 Christ redeemed us from the curse of the law by becoming a curse for us, because it is written, “Cursed is everyone who hangs on a tree,” 14 in order that the blessing of Abraham might come to the Gentiles in Christ Jesus, so that we might receive the promise of the Spirit through faith.
Finally salvation for all the earth
Isaiah 49:6 (LEB) — 6 And he says, “It is trivial for you to be a servant for me, to raise up the tribes of Jacob and to bring back the preserved of Israel.
I will give you as a light to the nations, to be my salvation to the end of the earth.”
1 Chron 16:23Sing to Yahweh,
all the earth! Proclaim his salvation from day to day!
