Paul warns the Gentile believers.
Paul, in the Romans 11:11 – 32, speaks to the Gentile Christians concerning their Jewish brothers in Christ. He reminds the Gentile Christians that the Jews did not “stumble beyond recovery.” Romans 11:11, NIV. Accordingly, Paul, an apostle to the Gentiles, warns his Gentile brothers in Christ not to be arrogant toward their Jewish brothers. “You will say then, ‘Branches were broken off so that I could be grafted in.’ Granted. But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but be afraid. For if God did not spare the natural branches, he will not spare you either.” Romans 11:19 – 21, NIV.
Paul reiterates that the Gentiles were a wild branch whom God grafted onto the natural olive tree. Therefore, the grafted wild branches draw their feed from the root of the root of the natural olive tree. Romans 11:17, NIV. The Gentile believers should be kind to the Jewish believers because the root of the tree feeds the branches; the branches do not supply root with food. The natural branches, which were broken off so that the wild branches could be grafted in, could be grafted back onto the cultivated tree, and thrive together with the wild branches that were grafted onto the natural olive tree. Jews rejected Jesus Christ, but He did not reject them; He died for the Jews also. Romans 11:24, NIV.
Paul quotes the Isaiah 59:20, 21, and 27:9, in support of the assertion that the “Israel was hardened until the full number of Gentiles has come in so, all Israel will be saved.” Romans 11:25, 26, NIV. While speaking about the destruction of the temple and Jerusalem, Jesus confirmed the same. “‘They will fall by the sword and will be taken prisoners to all the nations. Jerusalem will be trampled on by the Gentiles until the times of the Gentiles are fulfilled.'” Luke 21:24, NIV. The “all Israel” includes both, the Jews and the Gentiles who believe against all adds, like Abraham; are born from above, like Isaac; and like Jacob, persevere with God and hold on to Him no matter what.