Christ didn't teach that and Paul doesn't give any OT reference to back up his claim.
Christ says in no uncertain terms that he was "sent except [or only] for the lost sheep of the house of Israel (Mat 15:24), and he also explains what that means: no Gentiles and not even Samaritans (cf Mat 10:5-6). NT makes it equally clear that the witness to the Gentiles was not planned but a result of Israel's rejection of Christ (cf Act 13:46)— basically a "do or die" step.
The Old Testament surely doesn't seem to suggest that God predisgtined Israelites to fail, or that he wanted to be the God of the Gentiles. To the contrary. God of the OT is constantly sending his prophets to get Israel to come back to him. He makes no effort to convert the Gentiles, not even Ishmaelites (Arabas).
Let's face it, Paul had to do what he did because the Church was expelled from Israel, and, depsite his miracles, the Jews overall did not believe in Christ, nor for that matter that he even existed.
The Jewish rabbi by the name of Trypho is quoted as saying by Justin Martyr (c. 150 AD) [emphases added] "You follow an empty rumor and make a Christ [Savior] for yourselves ... If he was born and lived somewhere he is entirely unknown."–Justin Martyr the Phliosopher, Dialogue with Trypho
So, it's pretty obvious why Paul had to take up his swork to the Gentiles, and it wasn't any npredestination but Israel's rejection of Christ. The ministry to the Gentiles is simply not in the OT or in the Gospels. It is a knee-jerk reaction to the realities that ensued.
What of the Great Commission (Mt. 28:18-19)? "And Jesus coming, spoke to them, saying: All power is given to me in heaven and in earth. Going therefore, teach ye all nations; baptizing them in the name of the Father, and of the Son, and of the Holy Ghost."
And Acts 1:8? "But you shall receive the power of the Holy Ghost coming upon you, and you shall be witnesses unto me in Jerusalem, and in all Judea, and Samaria, and even to the uttermost part of the earth."
The ministry to the Gentiles is simply not in the OT or in the Gospels.
Also, what of Malachi 1:11, where the "clean oblation" is regarded to be the Eucharistic sacrifice? "For from the rising of the sun even to the going down, my name is great among the Gentiles, and in every place there is sacrifice, and there is offered to my name a clean oblation: for my name is great among the Gentiles, saith the Lord of hosts."
Old Testament Psalm 21 (22), the one Christ quotes on the Cross says, “All the ends of the world shall remember and turn unto the LORD: and all the kindreds of the nations shall worship before thee.
For the kingdom is the LORD’s: and he is the governor among the nations.”
And what of Isaiah 11:10? “And in that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek: and his rest shall be glorious.”
There are many others, but these come to mind at the moment.
GLORY TO CHRIST! AMEN!
Psalm 71 (72)--Messianic Psalm
[1] Give the king thy judgments, O God, and thy righteousness unto the king's son. [2] He shall judge thy people with righteousness, and thy poor with judgment. [3] The mountains shall bring peace to the people, and the little hills, by righteousness. [4] He shall judge the poor of the people, he shall save the children of the needy, and shall break in pieces the oppressor. [5] They shall fear thee as long as the sun and moon endure, throughout all generations. [6] He shall come down like rain upon the mown grass: as showers that water the earth. [7] In his days shall the righteous flourish; and abundance of peace so long as the moon endureth. [8] He shall have dominion also from sea to sea, and from the river unto the ends of the earth. [9] They that dwell in the wilderness shall bow before him; and his enemies shall lick the dust. [10] The kings of Tarshish and of the isles shall bring presents: the kings of Sheba and Seba shall offer gifts. [11] Yea, all kings shall fall down before him: all nations shall serve him. [12] For he shall deliver the needy when he crieth; the poor also, and him that hath no helper. [13] He shall spare the poor and needy, and shall save the souls of the needy. [14] He shall redeem their soul from deceit and violence: and precious shall their blood be in his sight. [15] 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. [16] 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. [17] 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. [18] Blessed be the LORD God, the God of Israel, who only doeth wondrous things. [19] And blessed be his glorious name for ever: and let the whole earth be filled with his glory; Amen, and Amen. [20] The prayers of David the son of Jesse are ended.
Those predestined to be conformed to the image of Christ are called into existence and justified through faith then glorified: "For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren. Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified. Romans 8:29-30.
God is the God of Israel, but also of the Gentiles (I'm not referring to what the Gentiles believed, but about God himself), and all--Jews and Gentiles alike, are justified by faith in Christ Jesus and not by Jewish observance of the law: "Therefore we conclude that a man is justified by faith without the deeds of the law. Is he the God of the Jews only? is he not also of the Gentiles? Yes, of the Gentiles also: Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith." Romans 3:27ff