I'm, of course, referring to Romans 11:26. Some people don't realize that the context of Romans 11 is established back in Romans 9. There is an overarching narrative that Paul taught starting at the beginning of Romans 9 through the end of Romans 11. In Romans 9, Paul establishes the fact that salvation is not based on one's nationality and that only a remnant of national Israel shall be saved rather than all of national Israel.
We can see that he taught that being a child of God and the spiritual seed of Abraham had nothing to do with being a physical descendant of Israel and of Abraham here...
Romans 9:6 It is not as though God’s word had failed. For not all who are descended from Israel are Israel. 7 Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” 8 In other words, it is not the children by physical descent who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring.
What Paul said in verse 6 is pretty straightforward. He spoke of two separate Israels and indicated that not all who are physically descended from the nation of Israel and physically descended from Abraham are part of Spiritual Israel and are Abraham's spiritual children/descendants.
Paul clarified that being part of spiritual Israel and being a spiritual child/descendant of Abraham was by way of being reckoned or called through Isaac, being a child of God and being a child of the promise. What does it mean to be reckoned through Isaac and to be a child of the promise and who does that apply to? We can see that by looking at other scripture that Paul wrote such as Galatians 4:21-28.
Galatians 4:26 But the Jerusalem that is above is free, and she is our mother. 27 For it is written: “Be glad, barren woman,you who never bore a child; shout for joy and cry aloud, you who were never in labor; because more are the children of the desolate woman than of her who has a husband.” 28 Now you, brothers and sisters, like Isaac, are children of promise.
To save space I didn't quote the whole passage, but you can read it for yourself and see that Paul was speaking in terms of two covenants here with one related to earthly Jerusalem and one related to heavenly Jerusalem. The thing to notice here is that Paul indicated that all believers are children of promise like Isaac because of having the heavenly Jerusalem as our spiritual mother rather than earthly Jerusalem, and that's what Paul is talking about in Romans 9:7-8 when explaining who they are exactly that are part of spiritual Israel. Those who are part of spiritual Israel are everyone who are the children of the promise like Isaac. Which is all believers because Paul was speaking to both Jew and Gentile believers in that passage.
Again, Paul indicated in Romans 9:6-8 that spiritual Israel consists of those who are children of the promise like Isaac and we can see what that means from Galatians 4:21-28. Paul also indicated that it is the children of God who are part of spiritual Israel, so determining who are the children of God can give us even more insight into who are in the Israel of which not all who descend from the nation of Israel are part.
Galatians 3:26 So in Christ Jesus you are all children of God through faith, 27 for all of you who were baptized into Christ have clothed yourselves with Christ. 28 There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. 29 If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.
Okay, so now we can see that the children of God are those who belong to Christ and they are the ones who are Abraham's seed and heirs according to the promise. That lines up with Romans 9:6-8 saying that those who are part of spiritual Israel are the children of God and the children of the promise who are counted as Abraham's offspring/seed.
So, the Israel of which all are saved and all will be saved is Spiritual Israel which does not include all of those who physically descend from national Israel and Abraham, but instead includes those from national Israel and from the Gentile nations who are the children of God by faith in Jesus since they are the ones who are the children of God and of the promise and are regarded as Abraham's spiritual seed.
Okay, so that all needs to be kept in mind as you continue reading the rest of Romans 9 and Romans 10 and into Romans 11. Paul continues the theme of showing that salvation is not dependent on one's nationality through the rest of Romans 9 and in Romans 10 and then into Romans 11.
Romans 9:23 What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24 even us, whom he also called, not only from the Jews but also from the Gentiles? 25 As he says in Hosea: “I will call them ‘my people’ who are not my people; and I will call her ‘my loved one’ who is not my loved one,” 26 and, "In the very place where it was said to them, ‘You are not my people,’ there they will be called children of the living God.’” 27 Isaiah cries out concerning Israel: “Though the number of the Israelites be like the sand by the sea, only the remnant will be saved.
See here how Paul talks about not just the Jews being called to salvation, but also the Gentiles and that those who were not God's people in the past would be called children of the living God just as Gentiles, who were formerly "without God in the world" (Ephesians 2:11-13) are now God's people (Gentile believers, obviously). And Paul points out that only a remnant of Israelites will be saved. Why would Paul say that a remnant of Israelites (not all Israelites) would be saved here in Romans 9:27, but then say that they will all be saved in Romans 11:26? That is contradictory and Paul wouldn't contradict himself.
Going from Romans 9 into Romans 10, Paul does not change the topic and reiterates the fact that one's nationality has nothing to do with salvation as it is available to both Jews and Gentiles alike with no difference between them.
Romans 10:12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.”
There is no difference between Jew and Gentile as it relates to salvation, so why would God ensure the salvation of every person in Israel without also doing that in the Gentile nations? By doing that it would suggest that there is a difference between Jew and Gentile in salvation, but that contradicts what Paul taught and contradicts the fact that God is not a respecter of persons (doesn't show favoritism because of things like one's nationality).
Then it moves from Romans 10 to Romans 11 where Paul proves that God did not cast away and reject the Israelites He foreknew, of which Paul himself was one, as evidenced by the fact that there was a remnant of elect believers in his day. The rest who didn't believe were temporarily blinded for the purpose of bringing salvation to the Gentiles so that those blinded Israelite unbelievers would be provoked to jealousy by the salvation of the Gentiles which would lead to the salvation of some of them, as Paul wrote about in Romans 11:11-14. You can read about everything I'm saying here in Romans 11:1-14.
After Romans 11:14, Paul creates an analogy of the things that he had been talking about up to that point since the beginning of Romans 9 by referring to a natural olive tree from which some of the natural branches, representing Israelite unbelievers, were cut off because of their unbelief. The natural branches that were not cut off stayed in the natural olive tree (the remnant of believers). Then Paul talked about wild branches from a wild olive tree being grafted in with the natural branches on the natural olive tree and that represents Gentile believers being saved by faith. And Paul talked about the natural branches that were cut off having the opportunity to be grafted in again, which refers to those who he said had been blinded, but he hoped to lead to salvation by way of provoking them to jealousy because of the salvation of the Gentiles (Romans 11:11-14).
So, that process of Israel being blinded in part (some being blinded and some not) with the hope of leading those who were blinded to salvation by being provoked to jealousy by the salvation of the Gentiles would continue until the fullness of the Gentiles comes in. Which leads us to this...
Romans 11:25 I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: Israel has experienced a hardening in part until the full number of the Gentiles has come in, 26 and in this way all Israel will be saved. As it is written: “The deliverer will come from Zion; he will turn godlessness away from Jacob. 27 And this is my covenant with them when I take away their sins.”
Now, when you read Romans 11:26 you can't forget that Paul already taught that only a remnant of national Israel would be saved, so does it make sense that he would contradict himself and then say that all national Israel will be saved? Of course not. You also can't forget that he had already spoke of another Israel consisting of the children of God and children of the promise who are regarded as the spiritual seed of Abraham. It's that Israel, which many of us call Spiritual Israel, of which all are and all will be saved. You can't interpret Romans 11:26 without taking into account the context that Paul had established in his narrative starting in Romans 9.
We can see that he taught that being a child of God and the spiritual seed of Abraham had nothing to do with being a physical descendant of Israel and of Abraham here...
Romans 9:6 It is not as though God’s word had failed. For not all who are descended from Israel are Israel. 7 Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” 8 In other words, it is not the children by physical descent who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring.
What Paul said in verse 6 is pretty straightforward. He spoke of two separate Israels and indicated that not all who are physically descended from the nation of Israel and physically descended from Abraham are part of Spiritual Israel and are Abraham's spiritual children/descendants.
Paul clarified that being part of spiritual Israel and being a spiritual child/descendant of Abraham was by way of being reckoned or called through Isaac, being a child of God and being a child of the promise. What does it mean to be reckoned through Isaac and to be a child of the promise and who does that apply to? We can see that by looking at other scripture that Paul wrote such as Galatians 4:21-28.
Galatians 4:26 But the Jerusalem that is above is free, and she is our mother. 27 For it is written: “Be glad, barren woman,you who never bore a child; shout for joy and cry aloud, you who were never in labor; because more are the children of the desolate woman than of her who has a husband.” 28 Now you, brothers and sisters, like Isaac, are children of promise.
To save space I didn't quote the whole passage, but you can read it for yourself and see that Paul was speaking in terms of two covenants here with one related to earthly Jerusalem and one related to heavenly Jerusalem. The thing to notice here is that Paul indicated that all believers are children of promise like Isaac because of having the heavenly Jerusalem as our spiritual mother rather than earthly Jerusalem, and that's what Paul is talking about in Romans 9:7-8 when explaining who they are exactly that are part of spiritual Israel. Those who are part of spiritual Israel are everyone who are the children of the promise like Isaac. Which is all believers because Paul was speaking to both Jew and Gentile believers in that passage.
Again, Paul indicated in Romans 9:6-8 that spiritual Israel consists of those who are children of the promise like Isaac and we can see what that means from Galatians 4:21-28. Paul also indicated that it is the children of God who are part of spiritual Israel, so determining who are the children of God can give us even more insight into who are in the Israel of which not all who descend from the nation of Israel are part.
Galatians 3:26 So in Christ Jesus you are all children of God through faith, 27 for all of you who were baptized into Christ have clothed yourselves with Christ. 28 There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. 29 If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.
Okay, so now we can see that the children of God are those who belong to Christ and they are the ones who are Abraham's seed and heirs according to the promise. That lines up with Romans 9:6-8 saying that those who are part of spiritual Israel are the children of God and the children of the promise who are counted as Abraham's offspring/seed.
So, the Israel of which all are saved and all will be saved is Spiritual Israel which does not include all of those who physically descend from national Israel and Abraham, but instead includes those from national Israel and from the Gentile nations who are the children of God by faith in Jesus since they are the ones who are the children of God and of the promise and are regarded as Abraham's spiritual seed.
Okay, so that all needs to be kept in mind as you continue reading the rest of Romans 9 and Romans 10 and into Romans 11. Paul continues the theme of showing that salvation is not dependent on one's nationality through the rest of Romans 9 and in Romans 10 and then into Romans 11.
Romans 9:23 What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24 even us, whom he also called, not only from the Jews but also from the Gentiles? 25 As he says in Hosea: “I will call them ‘my people’ who are not my people; and I will call her ‘my loved one’ who is not my loved one,” 26 and, "In the very place where it was said to them, ‘You are not my people,’ there they will be called children of the living God.’” 27 Isaiah cries out concerning Israel: “Though the number of the Israelites be like the sand by the sea, only the remnant will be saved.
See here how Paul talks about not just the Jews being called to salvation, but also the Gentiles and that those who were not God's people in the past would be called children of the living God just as Gentiles, who were formerly "without God in the world" (Ephesians 2:11-13) are now God's people (Gentile believers, obviously). And Paul points out that only a remnant of Israelites will be saved. Why would Paul say that a remnant of Israelites (not all Israelites) would be saved here in Romans 9:27, but then say that they will all be saved in Romans 11:26? That is contradictory and Paul wouldn't contradict himself.
Going from Romans 9 into Romans 10, Paul does not change the topic and reiterates the fact that one's nationality has nothing to do with salvation as it is available to both Jews and Gentiles alike with no difference between them.
Romans 10:12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.”
There is no difference between Jew and Gentile as it relates to salvation, so why would God ensure the salvation of every person in Israel without also doing that in the Gentile nations? By doing that it would suggest that there is a difference between Jew and Gentile in salvation, but that contradicts what Paul taught and contradicts the fact that God is not a respecter of persons (doesn't show favoritism because of things like one's nationality).
Then it moves from Romans 10 to Romans 11 where Paul proves that God did not cast away and reject the Israelites He foreknew, of which Paul himself was one, as evidenced by the fact that there was a remnant of elect believers in his day. The rest who didn't believe were temporarily blinded for the purpose of bringing salvation to the Gentiles so that those blinded Israelite unbelievers would be provoked to jealousy by the salvation of the Gentiles which would lead to the salvation of some of them, as Paul wrote about in Romans 11:11-14. You can read about everything I'm saying here in Romans 11:1-14.
After Romans 11:14, Paul creates an analogy of the things that he had been talking about up to that point since the beginning of Romans 9 by referring to a natural olive tree from which some of the natural branches, representing Israelite unbelievers, were cut off because of their unbelief. The natural branches that were not cut off stayed in the natural olive tree (the remnant of believers). Then Paul talked about wild branches from a wild olive tree being grafted in with the natural branches on the natural olive tree and that represents Gentile believers being saved by faith. And Paul talked about the natural branches that were cut off having the opportunity to be grafted in again, which refers to those who he said had been blinded, but he hoped to lead to salvation by way of provoking them to jealousy because of the salvation of the Gentiles (Romans 11:11-14).
So, that process of Israel being blinded in part (some being blinded and some not) with the hope of leading those who were blinded to salvation by being provoked to jealousy by the salvation of the Gentiles would continue until the fullness of the Gentiles comes in. Which leads us to this...
Romans 11:25 I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: Israel has experienced a hardening in part until the full number of the Gentiles has come in, 26 and in this way all Israel will be saved. As it is written: “The deliverer will come from Zion; he will turn godlessness away from Jacob. 27 And this is my covenant with them when I take away their sins.”
Now, when you read Romans 11:26 you can't forget that Paul already taught that only a remnant of national Israel would be saved, so does it make sense that he would contradict himself and then say that all national Israel will be saved? Of course not. You also can't forget that he had already spoke of another Israel consisting of the children of God and children of the promise who are regarded as the spiritual seed of Abraham. It's that Israel, which many of us call Spiritual Israel, of which all are and all will be saved. You can't interpret Romans 11:26 without taking into account the context that Paul had established in his narrative starting in Romans 9.