Romans 11:26 says, “And in this way all Israel will be saved.” I take this to mean that someday the nation as a whole (not necessarily every individual; see 1 Kings 12:1; 2 Chronicles 12:1) will be converted to Christ and join the Christian church and be saved.
This was J. C. Ryle’s view published in 1867:
[The Jews] are kept separate that they may finally be saved, converted and restored to their own land. They are reserved and preserved, in order that God may show in them as on a platform, to angels and men, how greatly he hates sin, and yet how greatly he can forgive, and how greatly he can convert. Never will that be realized as it will in that day when “all Israel shall be saved.” (Are You Ready for the End of Time? [Ross-shire, Scotland: Christian Focus Publications, 2001], 137–138)
One reason this matters is that Paul made this claim “lest you [Gentiles] be wise in our own sight” (Romans 11:25). Rightly understanding the historical process of how God saves Gentiles and Jews undercuts Jewish and Gentile pride.
So here are five of the reasons I commend this view to you. You can read other arguments for the same position in the commentaries of John Murray, John Stott, Douglas Moo, and Thomas Schreiner.
1. The term “Israel” in verses 25 and 26 most naturally refers to the same thing.
Verse 25: “Lest you be wise in your own conceits, I want you to understand this mystery, brothers: a partial hardening has come upon Israel. . . .” That must refer to the nation as a whole from generation to generation. He continues, “. . . until the fullness of the Gentiles has come in. (26) And in this way all Israel will be saved.” I don't think the meaning of Israel changes between verses 25 and 26. The hardened Israel (the nation as a whole) will be the saved Israel (the nation as a whole).
2. The reference in verse 26 to banishing ungodliness from Jacob fits with the national view of “all Israel.”
Verse 26: “And in this way all Israel will be saved, as it is written, ‘The Deliverer will come from Zion, he will banish ungodliness from Jacob.’” This seems most naturally to be a picture of the second coming. Christ’s banishing ungodliness from Jacob refers most naturally to the removal of the hardening referred to in verse 25. “Jacob” is not a natural or typical reference to the elect remnant of Israel. The hardening lasts until the full number of the Gentiles comes in (the climax of world missions), and then Christ lifts the veil and removes the hardening — he banishes ungodliness from Jacob, from “all Israel.”
3. The parallel between the two halves of verse 28 point to all Israel as the nation as a whole.
Verse 28: “As regards the gospel, they are enemies of God for your sake.” Now this half of the verse surely refers to the nation as a whole — they are enemies of God. So the second half of the verse surely refers to the nation as a whole as well: “But as regards election, they are beloved for the sake of their forefathers.” The point of this verse is to show that even though Israel now is a covenant-breaking, unbelieving nation, it is going to change. The nation that are enemies now will be converted later because of election and love.
4. The parallels in verse 12 point in the same direction.
Verse 12: “Now if their [the Jewish nation’s] trespass means riches for the world [salvation for the Gentiles], and if their [the Jewish nation’s] failure means riches for the Gentiles, how much more will their full inclusion!” Here “their full inclusion” most naturally refers to the same nation as “their trespass” and “their failure.” So “their full inclusion” refers to the salvation of “all Israel” and is national.
5. The same thing is true about the parallels in verse 15.
“For if their [Jewish nation’s] rejection means the reconciliation of the world, what will their [Jewish nation’s] acceptance mean but life from the dead?” The nation now rejected will be accepted. So the “acceptance” of the Jewish nation most naturally refers to the salvation of “all Israel” — the salvation of the nation as a whole some day.
How is this going to happen? I don't know the details, but it seems to me that Paul does mean that in connection with the second coming of Christ there will be a great turning of Israel to Christ. Just how it works, I don't know. But I find certain prophecies very suggestive.
For example, Zechariah 12:10, “And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that, when they look on me, on him whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn.” And Isaiah 66:8, “Who has heard such a thing? Who has seen such things? Shall a land be born in one day? Shall a nation be brought forth in one moment? For as soon as Zion was in labor she brought forth her children.” And Matthew 23:39, where Jesus says to the hardened nation: “I tell you, you will not see me again until you say, ‘Blessed is he who comes in the name of the Lord.'”
I don't want to speculate about details we are not given. I am not sure about the precise "when and how" of Israel's conversion. But that it is coming and that it will be given by Jesus Christ, the deliverer who banishes ungodliness and forgives sins — I feel sure.
We should pray for it — that the full number of the Gentiles comes in and that the hardening be lifted from Israel. We should work for it with missions to the nations and witness to Israel. We should put away all conceit and presumption over Jewish unbelievers but realize that God is aiming to save them through our salvation.
For now, then, let us give ourselves to prayer and to the great work of gathering the fullness of the Gentiles, if by any means we might make Israel jealous of her treasures in Christ so that they believe and be saved.