Romans 1-3; 9-11, and 15, are talking about with regard to the status of the faith of God's Word as to His plan and purpose in Himself through His Son by the Spirit as to Israel.
Romans 3
1. What advantage then hath the Jew? Or what profit is there of circumcision?
2. Much every way: chiefly, because that unto them were committed the oracles of God.
3. For what if some did not believe? Shall their unbelief make the faith of God without effect?
Romans 9
4. Who are Israelites; to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises;
5. Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen.
6. Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
7. Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
What God purposed in Himself to do as to all the above through His Son by the Spirit in that nation had
not failed.
It only appeared to have failed -
Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
Romans 11 continues this thought - what happened with Israel that it appears God was now through with His purpose in Himself through them as to all that?
Romans 11
1. I say then, Hath God cast away his people? God forbid. For I also am an Israelite, of the seed of Abraham, of the tribe of Benjamin.
I'm sorry, but that passage is literal! The fact is that...
2. God hath not cast away his people which he foreknew. Wot ye not what the scripture saith of Elias? How he maketh intercession to God against Israel saying,
3. Lord, they have killed thy prophets, and digged down thine altars; and I am left alone, and they seek my life.
4. But what saith the answer of God unto him? I have reserved to myself seven thousand men, who have not bowed the knee to the image of Baal.
Those were seven thousand sons of Jacob!
Well guess what? You see that principle - Israelites - sons of Jacob?
5. Even so then at this present time also there is a remnant according to the election of grace.
6. And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then it is no more grace: otherwise work is no more work.
7. What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded.
This election of grace is not ours here - he is talking about the sons of Jacob who chose to believe the God of their fathers.
He is talking about this promise ---
Exodus 19
3. And Moses went up unto God, and the LORD called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel;
4. Ye have seen what I did unto the Egyptians, and how I bare you on eagles' wings, and brought you unto myself.
5. Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine:
6. And ye shall be unto me a kingdom of priests, and an holy nation. These are the words which thou shalt speak unto the children of Israel.
7. And Moses came and called for the elders of the people, and laid before their faces all these words which the LORD commanded him.
8. And all the people answered together, and said, All that the LORD hath spoken we will do. And Moses returned the words of the people unto the LORD.
Verse 8 "all the people" entered into that, but "not all" followed suit.
Romans 9-11 says very little about the Body of Christ because Paul is dealing with the issue of what became of God's faith to His Word as to Israel's adoption, and glory, and the promises, and all the rest.
That despite how things looked, it was...
6. Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
7. Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
He is relating the principle that things do not look as they appear.
And he is relating that to us Gentiles even now, thus his words in
Romans 11
25. For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
You need to carefully restudy all this out in light of the passages
alone.