For if their being cast away [is] the reconciling of the world, what [will] their acceptance [be] but life from the dead? For if the firstfruit [is] holy, the lump [is] also [holy]; and if the root [is] holy, so [are] the branches. And if some of the branches were broken off, and you, being a wild olive tree, were grafted in among them, and with them became a partaker of the root and fatness of the olive tree, do not boast against the branches. But if you do boast, [remember that] you do not support the root, but the root [supports] you. 19 You will say then, "Branches were broken off that I might be grafted in." Well [said]. Because of unbelief they were broken off, and you stand by faith. Do not be haughty, but fear. 21 For if God did not spare the natural branches, He may not spare you either. Therefore consider the goodness and severity of God: on those who fell, severity; but toward you, goodness, if you continue in [His] goodness. Otherwise you also will be cut off. And they also, if they do not continue in unbelief, will be grafted in, for God is able to graft them in again. For if you were cut out of the olive tree which is wild by nature, and were grafted contrary to nature into a cultivated olive tree, how much more will these, who [are] natural [branches], be grafted into their own olive tree? For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in. And so all Israel will be saved, as it is written: "The Deliverer will come out of Zion, And He will turn away ungodliness from Jacob; For this [is] My covenant with them, When I take away their sins." Concerning the gospel [they are] enemies for your sake, but concerning the election [they are] beloved for the sake of the fathers. For the gifts and the calling of God [are] irrevocable. For as you were once disobedient to God, yet have now obtained mercy through their disobedience, even so these also have now been disobedient, that through the mercy shown you they also may obtain mercy. For God has committed them all to disobedience, that He might have mercy on all. Romans 11:15-32
But although He had done so many signs before them, they did not believe in Him, that the word of Isaiah the prophet might be fulfilled, which he spoke: "Lord, who has believed our report? And to whom has the arm of the LORD been revealed?" Therefore they could not believe, because Isaiah said again: "He has blinded their eyes and hardened their hearts, Lest they should see with [their] eyes, Lest they should understand with [their] hearts and turn, So that I should heal them." John 12:37-40