This is taken from a misinterpretation of Romans 11. Romans 11 does not tell us that the Gentiles have been grafted into Israel. Romans 11 tells us that we have been grafted into the Olive tree to be a partaker of the root and the fatness (which represents God in Christ) (Rom 11:17) .
As Gentiles, we were cut out of a wild Olive tree and grafted contrary to our nature to the things of God, but Israel is quite at home, said to be a “natural branch.” Israel is a natural branch and the gentiles are a wild branch which he can cut off or graft into the olive tree which is Christ (Rom 11:24).
These are separate branches. The argument in Romans 11 is that:
- The branch of Israel was cut off before the gentiles were grafted in.
- Israel is certain to be grafted back in, and all Israel will be saved. When they do, it will be because of the covenant that He has made with them (as a nation) to forgive their sins (Romans 11:25-26).
- Paul’s argument in Romans is that the only reason the Gospel is moving among the Gentiles is because the natural branch was cut off. If we were grafted into the natural branch, we would also be “cut off”. Partial blindness has come upon Israel until the fullness of the Gentiles comes in, and then all Israel shall be saved (Romans 11:25)
Paul tells us clearly in Romans that the covenants belong to Israel (Romans 9:4). In Ephesians Paul tells us that Gentiles had no part in any covenants, but were aliens to them and strangers (Eph 2:12). The blood of Christ reconciles us to God in the Body of Christ, a new creation, in which there is no Jew or Greek but Christ is all and in all (Col 3:10-11). Our connection to any covenant because we have been baptized into Abraham’s seed, which is Christ and have become heirs (not parties to a covenant). (Gal 3:16; Gal 3:26-29). We have not become part of national Israel to be partaker of a covenant the Christ will mediate with them.