Here’s a mystery: The nation Israel and the Church are both part of God’s plan for the world. Whilst talking to the Jews, Jesus said:
“I have other sheep, too, that are not in this sheepfold. I must bring them also … and there will be one flock with one shepherd” (John 10 verse 16, NLT)”
The “other sheep” are Gentiles believers. Jesus was referring to the Gentile church.
The apostle Paul symbolizes this future joining of Jewish and Gentile believers through the allegory of the olive tree. Paul likened Israel to natural olive branches of a cultivated olive tree (Romans 11.24). The tree itself is rooted in the Patriarchs, particularly Abraham, and ultimately in Jesus. The ‘cultivation’ is seen in the Abrahamic covenants, and so the Jewish nation was placed under a program governed by covenants.
On the other hand, Gentile believers are like wild olive branches in that they had no covenants (Ephesians 2.11-12). In the future both the natural branches (believing Jews) and the wild branches (Gentile believers) will be grafted together into the olive tree (Christ). Why? Because the olive tree represents the place of blessing in God’s plan. Jesus said:
I am the vine, and you are the branches. Those who remain in me, and I in them, will bear much fruit; for you can do nothing without me (John 15 verse 5)
This verse applies to believing Gentiles (the true church) and to the people of Israel (which we have loosely called ‘Jews’):
And this is how all Israel will be saved. As the scripture says, “The Savior will come from Zion and remove all wickedness from the descendants of Jacob. I will make this covenant with them when I take away their sins” (Rom 11 verses 26-27)
See also Israel and the Church