There is an interesting and sometimes confusing mystery found in Romans 11:25-29. The text says, “Lest you be wise in your own sight, I do not want you to be unaware of this mystery, brothers: a partial hardening has come upon Israel, until the fullness of the Gentiles has come in. 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”; “and this will be my covenant with them when I take away their sins.” As regards the gospel, they are enemies for your sake. But as regards election, they are beloved for the sake of their forefathers. For the gifts and the calling of God are irrevocable.”
I believe the mystery of Romans 11:25-29 is that Israel has been placed in abeyance. Israel was the chosen people and nation of God and as such, they had many promises made to them that are yet to be fulfilled completely (Gen. 12:1-3; 15:12-21; 22:17-18; 2 Sam. 7:1-17). Being in abeyance means that they have been placed in a state of suspension.
It is like saying my grandad owned a large ranch but decided to lease it out. Now say this lease is a life-time lease that only expires upon the death of the one who leased it, or at 99 years. Now, say my grandad dies, with half the least still to go but left the ranch to my dad and uncle. They cannot legally take the ranch as theirs until the lease is up, the man leasing dies, or he turns it over. The land legally belongs to my dad and uncle but they cannot do anything on it until the lease is over. This is the mystery. Israel is still the chosen nation and people of God, they have just rejected the Messiah and did not keep God’s statutes as laid out in Deuteronomy 28-29. So, the ranch is not theirs until the lease is up, or until the fullness of Gentiles has come in (ESV Rom. 11:25).
The Israelites were warned that this would happen in Deuteronomy, “A nation that you have not known shall eat up the fruit of your ground and of all your labors, and you shall be only oppressed and crushed continually…all these curses shall come upon you and pursue you and overtake you till you are destroyed, because you did not obey the voice of the Lord your God, to keep his commandments and his statutes that he commanded you” (28:33,45). Also, as the Lord said in Hosea, “I will say to Not My People, You are my people…” (2:23) as Paul phrases it in Romans, “Those who were not my people I will call my people and her who was not beloved I will call ‘beloved’” (9:25).
So, this mystery was not really concealed as many mysteries are. Henry C. Thiessen states, “A part of this mystery is the ‘hardening’ that God has permitted to come and even judicially sent to some of Israel.” Israel was warned that this would happen way back in the time of the Exodus. They had just become so wrapped up in them being the chosen people and because of being so they were okay. Paul is telling them differently.
Even though they are set aside for now, “the gifts and the calling of God are irrevocable” (Rom. 11:29). This is a reference to the promises of God to the patriarchs. In Gen. 12:1-3; 15:12-21; 22:17-18 we see the promises to Abraham that he will be the father of a great nation and that God is giving them the land (Gen. 15:18). God made the covenant by His word and deed, this required nothing of man.
This is seen in the fact that Abraham was sleeping when God passed between the split apart animals. Also, Hebrews tells us, “For when God made a promise to Abraham since he had no one greater by whom to swear, he swore by himself…” (6:13). Another promise that God made with Abraham was, “all the land that you see I will give to you and your offspring forever” (Gen. 13:15). Also, God promised David that a king, kingdom, and throne would be established forever from his lineage (2 Sam. 7:12-17). God made promises and because of God’s pledged word to the patriarchs, he will not annul Israel’s election. And God is not a man that He should lie or break promises or change what He said He will fulfill (Num. 23: 19; 1 Sam. 15:29; Mal. 3:6; Rom. 11:29; Titus 1:2; Heb. 6:18; James 1:17).
This, then, leads to “all Israel will be saved” (Rom. 11:26). I believe this means the totality of Israel. The nation, not necessarily every individual Israelite. I believe since all of these promises to Israel have only partially been fulfilled that God is going to turn His attention back to Israel again. I hold this view, not only because these promises have not been fully fulfilled, but, also, because of certain texts in the prophets of the OT. In Ezekiel, we see where God tells the nation that he will gather them back to their land and cleanse them of all uncleanness and their idols and that He will make the land into an overly abundant land with no famines (36:22-38).
Not only these verses but in the next chapter God promises that the nations of Israel and Judah will be one nation again with one king over them, that David shall be king over them, that they will live in the land that God gave them forever, and that God will set His sanctuary “in their midst forevermore” (37:21-27). Now, again, this does not mean that every single Jew will be saved. It does mean that national Israel will once again be God’s people and they will receive all their promises and blessings.
God does not lie nor does He break His promises (Num. 23:19; Titus 1:2; Heb. 6:18), and I believe that he will make good these promises. For this to happen there has to be an Israel from Abraham and for this to happen God has to turn back to the nation Israel. As the text says, “a partial hardening has come upon Israel until the fullness of Gentiles has come in…as regards election, they are beloved for the sake of their forefathers” (Rom. 11:25,28).
They are partially hardened until the full number of Gentiles comes in, the lease is up, then Israel will once again be the ones in the hot seat and receiving their final cleansing until those who will be saved are saved and the land will be theirs. “All Israel will be saved” as in the nation, not strictly individuals. There is still one week in the prophecy of Daniel that is to be fulfilled, and this will come when the fullness of Gentiles comes in (Dan. 9:24-27). This is when Israel will be saved and cleansed as the prophecy of Ezekiel states.
I believe the promises were made to Israel, not the Gentiles. The Israelites are the chosen people of God. We are the church and have not replaced Israel. There is still a plan for Israel that is yet to be completed.
 Henry C. Thiessen, “The Place of Israel in the Scheme of Redemption: As Set Forth in Romans 9-11,” Bibliotheca Sacra 98/389 (1941): 203-17.