Gentiles were grafted in.
Equal partners (Romans 10:12) both groups are "one" (Ephesians 2:14).
God made no covenant with Gentiles or any Gentile and his seed.
Here, these are examples of a Covenant. Show me in the Jewish Scriptures God making any kind of Covenant with Gentiles.
Here. Here's a Covenant God made with covenant language:
11 And
I will establish my covenant with you; neither shall all flesh be cut off any more by the waters of a flood; neither shall there any more be a flood to destroy the earth. Gen. 9:11.
See that? That's a covenant with covenant language. Here's another:
7 And
I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee.
Gen. 17:6–7.
See that? That's a covenant with covenant language. Here's another:
8 And Moses took the blood, and sprinkled it on the people, and said,
Behold the blood of the covenant, which the LORD hath made with you concerning all these words. Ex. 24:8.
See that? That's a covenant with covenant language. Here's another:
3
I have made a covenant with my chosen,
I have sworn unto David my servant,
4 Thy seed will I establish for ever,
And build up thy throne to all generations. Selah.
Ps. 89:3–4.
See that? That's a covenant with covenant language. Here's another:
31
Behold, the days come, saith the LORD,
That I will make a new covenant
With the house of Israel, and with the house of Judah:
Jer. 31:31.
See that? That's a covenant with covenant language. In all these instances you see the language of covenant, God intending a covenant and actually making it, and Hebrews/Jews as recipient of the Covenant God makes with a certain people and that people are Hebrews/Jews and the children of Israel and David who is a Jew. And there's one more covenant. More like an anti-covenant. A direct command for Israel to make NO COVENANTS with anyone else except God and that's because as Bride of Christ, to make a covenant with anyone else besides their betrothed is adultery. And God is a jealous God.
31 And I will set thy bounds from the Red sea even unto the sea of the Philistines, and from the desert unto the river: for I will deliver the inhabitants of the land into your hand; and thou shalt drive them out before thee.
32
Thou shalt make no covenant with them, nor with their gods. Ex. 23:31–32.
So, for you to say Gentiles that come to Christ are joined equally in covenant with the children of Israel is a lie. God forbids it. God commands against it. And Paul is surely, as apostle of Jesus Christ, NOT teaching it nor advocating it. So this means your interpretation of Saul/Paul's words are in error.
God made no covenant with Gentiles nor any Gentile and their seed, nor has God joined Jew and Gentile in any covenant at all.
THE WORD OF GOD.
Receive or reject. There is no medium.