Believers of the nations are grafted onto the olive tree (Romans 11). Does this mean that they are incorporated into Israel?
Believers of the nations, together with believers of Israel make up “one body” (1Cor.12:13; Eph.2:16), of which Christ is the Head (Col.1:18; Eph.1:22). That body is a formation, which, by definition, could not commence earlier than since the death and resurrection of Christ. Regardless how many similarities there are to enumerate, the ecclesia (the body of Christ) on the one hand and the people of Israel on the other hand, are two different peoples. Also, the destiny of both peoples differ from each other as heaven and earth. Israel, as a people, is destined for the Kingdom of Peace on earth, to be a channel of blessings (Amos 9:11-15), while the ecclesia, as a heavenly people, will be placed over heaven and earth (Ephesians 1:3,10,11).
Paul, in his letter to the Romans, does not state that the believers of the nations are incorporated into Israel, but that
… the nations participate in their (=Israel’s) spiritual things…
That is something very different! Paul asks in Romans 3:1, What is the advantage of the Jew? and answered this question himself with:
Much in every manner. For first, indeed, that they were entrusted with the oracles of God.
The possession of the words of God is a privilege that the Jew has naturally, in contrast to the nations (Ps.147:19.20). Through Paul’s ministry, however, the nations have become partakers of these spiritual goods of the people of Israel. Thus they are grafted onto the olive tree and so they became joint participants of the “fatness” of the olive (Rom.11:17). Olive oil in Scripture represents the living, vital words of God, meant to spread light (>oil in the lamps).
Summarized: the olive tree in Romans 11 stands for the spiritual goods of Israel.
Translation: Peter Feddema