The Word of God teaches us how we are to understand the relationship between the Old and New Testament, which relates to the relationship between the Jews and Gentiles. If we let go of certain preconceived ideas, that relationship is not difficult to grasp.
"For if the first fruit be holy, the lump is also holy: and if the root be holy, so are the branches. And if some of the branches be broken off, and thou, being a wild olive tree, were grafted in among them, and with them partakest of the root and fatness of the olive tree . . ." (Rom. 11:16-36).
The illustration Paul uses here is not a complex one. God has a cultivated olive tree, on which the Jews were natural branches. In the first century, many of them were cut out because of their unbelief, and wild olive branches (the Gentiles) were grafted in. The Gentiles were warned that the methods for tending the tree have not changed between Malachi and Romans, so the ingrafted branches must be characterized by faith and humility. If they fall into the sin of presumption, as many of the Jews did, the same thing could happen to them.
God had granted enormous privileges to the nation of Israel, which Paul had recounted earlier in Romans. First, Israel was a teacher. "An instructor of the foolish, a teacher of babes, which hast the form of knowledge and of the truth in the law"(2:20). Second, the Jews had been entrusted with Scripture; they were the appointed custodians of the Scriptures. "What advantage then hath the Jew? or what profit is there of circumcision? Much every way: chiefly, because that unto them were committed the oracles of God" (3:1-2). Third, they also had a range of gifts, their privileges were far-reaching. Of particular interest was their possession of the covenants and the promises. "Who are Israelites; to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises; whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen" (9:4-5).
These privileges were enormous, but they were not limitless and unconditional. The carnal heart also wants covenant privileges to be automatic privileges, and they never are. If we follow Paul carefully here, we will see that the covenant with the Jews profited them if . . . The covenant reality is far more important than the covenant sign of that reality. To obey is better than sacrifice. "For circumcision verily profiteth, if thou keep the law: but if thou be a breaker of the law, thy circumcision is made uncircumcision . . ." (2:25-29). The terrible judgment described in chapter 11, and the stern warning to the Gentiles there, is based on cumulative warnings that were gathering throughout the entire book. Our difficulty in getting this warning is based on a very natural, carnal tendency. It is not that Paul was murky -- it is that our hearts are murky.
The covenant people -- Jews in the Old Testament and Christians in the New -- were, and are, and will be until the Last Day, a mixed multitude. Throughout the Old Testament, there were Jews who were Jews and there were Jews who weren't. Throughout the aeon of the new covenant, the same thing is true -- there are Christians who are Christians and there are Christians who aren't. Why is this so hard to understand?On any other supposition, Paul's stern warning in Romans 11 would is senseless. God always has an Israel within Israel.
God remains true even if every man is a liar -- even if every covenant member is a liar. Here is the answer of God. However bad the conditions might be, God’s Word stays firm. "But what saith the answer of God unto him? I have reserved to myself seven thousand men, who have not bowed the knee to the image of Baal. Even so then at this present time also there is a remnant according to the election of grace" (11:4-5). Not all Israel is Israel. Not all the new Israel is the new Israel. We must distinguish between sons of the covenant, and sons indeed. "Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel: Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called" (9:6-7).
Many Christians agree with this principle so long as we are talking about somebody else. They think this is a fine system for the Jews. Apply it to the Church and they go sideways. But -- and this is the central point, as well as an obvious one -- the engrafting of the Gentiles has not changed the nature of the tree. Paul's whole argument depends on the nature of the tree remaining constant. Branches are cut out in the old covenant, and they can just as easily be cut out in the new. We need to learn to take Paul's illustration at face value. When this olive tree illustration is taken at face value, a multitude of theological and doctrinal problems are solved. The exhortation is therefore to take it at face value.
Covenant membership is not decretal election. But neither is covenant membership a nullity. Understanding one's place in the covenant is essential to full-orbed discipleship. If a covenant member can apostatize, and many have, what use is infant baptism then? . . . much in every way. God's gifts and calling remain irrevocable, and this even applies to the Jews, two thousand years later. "Hath God cast away his people? God forbid . . ." (11:1-2a; cf. 11:11). God has promised that His covenant blessings will come to emcompass the whole world, and the conversion of the Jews as they return to their Messiah is an important part of this. That being the case, we should all be a lot more optimistic about the future of the olive tree than we actually are.