Romans 11:5-7, 23-24, 28-32

Even so then at this present time also there is a remnant according to the election of grace. And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work. What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded

And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again. For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?

As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes. For the gifts and calling of God are without repentance. For as ye in times past have not believed God, yet have now obtained mercy through their unbelief: even so have these also now not believed, that through your mercy they also may obtain mercy. For God hath concluded them all in unbelief, that he might have mercy upon all.