God's Word itself clearly teaches that Israel was a typical representation and what was said of Israel now directly applies to the True Christian congregation.
Peter applies what was said of Israel to Christians (Ex. 19:5-6 / 1 Pet. 2:9-10). Paul shows that what was said of Israel now applies to an "Israel" which has nothing to do with whether one is a natural Jew or not (Gal. 3:26-29; 6:16; Mt. 3:9; 21:42-43). Replacing natural Israel as God's nation, it becomes a new "Israel" that is "really 'Israel'" (Rom. 2:28-29; 9:6-9).
It is clear that "Although the number of the sons of Israel may be as the sand of the sea, it is the remnant that will be saved" (Rom. 9:27).
So "only a remnant" of natural Israel will be saved and NOT Israel as a nation. Jews would have to become Christian and accept Christ. John's vision of those on the heavenly Mount Zion revealed the spiritual Israel of God to be 144,000 "bought from among mankind" not "from among the Jews" (Rev. 7:4; 14:1,4; 5:9,10; Jas. 1:1).
Paul said that natural "Israel" is not "really Israel" (Rom. 2:28-29; 9:6-9).
Rom. 11:1,2 says: "God has not rejected his people whom he foreknew" but, the context makes it clear that salvation would not be given to Israel as a "nation" but only to a "remnant," and only to the "ones chosen" as contrasted with "the rest" who were blinded. Paul only held out a hope to "save some from among them" (Rom. 11:5-14).
(Jehovah's) Witnesses know that the primary fulfillment of the N(ew) T(estament) statements are directed at spiritual Israel and the Gentile nations.
Speaking to the Jewish religious leaders; Jesus said: "This is why I say to YOU, The kingdom of God will be taken from YOU and be given to a nation producing its fruits (Matt. 21:42-43). Replacing natural Israel as God's nation, it becomes a new "Israel" that is "really 'Israel'" (Rom. 2:28-29; 9:6-9).
John's vision of those standing on the heavenly Mount Zion with the Lamb revealed the number of this spiritual Israel of God to be 144,000 "bought from among mankind" not "from among the Jews (Rev. 7:4; 14:1, 4; 5:9,10; James 1:1).
As God's covenant people, these natural Jews had the first opportunity to be part of the New Covenant to rule as kings in heaven (Acts 3:25,26; Rom. 1:16; Heb. 8:7-13). However, as a nation, Israel failed to fill up that number (John 1:10-13; Acts 13:46; Rom. 9:27; 11:7-10). Later, so that the "full number of those sealed" would be completed the invitation was extended to non-Jews (Isa. 55:5; Acts 10:44-45; 15:14; Rom. 11:25; 15:14; Eph. 2:11-13; 3:1-6; Rev. 5:9-10; 7:4). Jews could only get another chance by becoming Christian and accepting Christ. John's vision of those standing on the heavenly Mount Zion with the Lamb revealed the number of this spiritual Israel of God to be 144,000 "bought from among mankind" not "from among the Jews (Rev. 7:4; 14:1, 4; 5:9,10; James 1:1).
The restoration prophecies of Ezekiel, Jeremiah and Isaiah are in line with the prophecies of Christ regarding the complete restoration of True Worship that would come at the "time of the end" (Acts 3:20- 21; 20:29-30; Luke 19:11,12; Mt. 25:21-30; 2 Thess. 2:3-12; 1 Tim. 4:1; 2 Pet. 2:1-3).
At "the conclusion of the system of things...the righteous ones would then shine as brightly as the sun" (Mt. 13:24-30, 36-43; 24:45-47; Dan. 12:1,3,4,10).
By their biblical beliefs and Christlike actions, Jehovah's Witnesses prove that they are fulfilling the restoration prophecy of Ezekiel regarding faithful spiritual Israel. This is the testimony of the Holy Spirit (1 Cor. 6:9-11; Gal. 5:19-22).
(Source: This is the answer given by Bar_Anerges to this question.)