I have been thinking about several things these days and one of those things has to do with the relationship between the people of God in the Old Testament (OT) and the people of God in the New Testament (NT). I hope you will find what follows to be of interest. It is an attempt to look at the continuity between the church age and the ages that came before.
Question: Are Christians a totally separate people of God than those under the Old Covenant?
Answer: No. We are part of the one covenant people of God. There is only one people of God from the time of Adam until the Second coming of Jesus Christ.
We know this because Paul tells us that we gentiles have been grafted into the one olive tree, which represents God's covenant people (i.e. Israel). We are not a new tree (a new people) we are but branches grafted in with those that were already there (the ethnically Jews Christians) and were not cut off for unbelief.
For if the firstfruit 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, wert graffed in among them, and with them partakest of the root and fatness of the olive tree; Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee. Thou wilt say then, The branches were broken off, that I might be graffed in. Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear: For if God spared not the natural branches, take heed lest he also spare not thee. (Romans 11:16-21)
This shows our continuity with the Old Covenant (OC) people of God. Notice that some of God's covenant people were broken off of the olive tree. These were the Jews who rejected Christ. They were in covenant and yet not saved. We non-Jews in the New Covenant, represented as wild branches, were grafted in to the very same olive tree. This means we have become part of God's one covenant people. Notice also that we too are threatened with the possibility of being cut off just as they were.
I am not an Arminian, so I don't believe a born again individual can loose his or her salvation. If those now in the New Covenant (NC) era can be cut off of the Olive tree in the same way those in the OC were cut off, then it follows that there are some of God's covenant people today who are not born again. They, like those in the OC, can be cut off.
The fact that we are "grafted into the olive tree" and are part of the one people of God is a strong point of continuity that exists under all the separate covenants, from the beginning of history to the end.
I would like you to notice something else from Romans 11. "And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree; Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee." (Romans 11:17)
Notice we partake of the root. We partake of the ancient covenants and promises. We are not something brand new. We Christians are united to the ancient root of God's covenant people. Not only that but "thou bearest not the root, but the root thee." It is the ancient root of the one people of God that supports us here in the NC.
We Christians are also (like believing ethnic Jews) "Abraham's seed, and heirs according to the promise" (Gal, 3:29). We are fixed here directly to God's covenant with Abraham. We in the church are the heirs of God's promises to Abraham. This again connects us today with the ancient people of God. God's people both then and now, are one people not two or more. We are part of the Covenant people of God, and are therefore sons of the Abraham whom God gave His covenant sign to.
Now let's go to Ephesians. Here we read "Wherefore remember, that ye being in time past Gentiles in the flesh, who are called Uncircumcision by that which is called the Circumcision in the flesh made by hands; That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world: But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ." (Eph. 2:11-13)
Notice that we "being in time past Gentiles in the flesh" are no longer so. We are no longer Gentiles. Why? Because we are now part of the one covenant people of God. We who were "aliens from the commonwealth of Israel, and strangers from the covenants of promise" are no longer so. We are no longer aliens from the commonwealth of Israel.
Question: What is a commonwealth?
Answer: The Greek word translated commonwealth here is "politeia", and it can be defined as "a state or commonwealth" and as "citizenship."
So we are no longer aliens to the "state," "commonwealth, or "citizenship" of Israel. We, who were once gentiles, are now citizens of God's covenant people Israel, and are part of the historic covenant people of God.
Notice that we, who were once gentiles, are no longer strangers from the "covenants" (plural) "of promise" (singular).
Question: Who were these "covenants" made with?
Answer: They begin at the beginning. In Genesis 3 is where we find the first of these covenants; next it is with Noah; then Abraham, Moses, David and then the New Covenant with the house of Israel and house of Judah.
We who were once gentiles are now no longer "strangers from the covenants of promise." Why is that? It is because we have been grafted into the one people of God. We have become citizens of the commonwealth of Israel. This is continuity with the old covenants that were all part of the one promise.
The radical discontinuity between OC and NC that some modern Christians perceive is (IMHO) a gross misreading of the Word of God.
We, in the church are today the Israel of God. This is why we in the church are a "holy nation" (1 Pet 2:9) just as our fellow citizens in ancient Israel were a "holy nation" (Ex. 19:6). Israel was the "peculiar people" of God (Deut 14:2; 26:18) and we in the church today are also the "peculiar people" of God (Titus 2:14; 1 Pet. 2:9).
These examples that are given above are just a few of the Scriptures that show continuity between the people of God in the OC and the People of God in the NC. They can be expanded many times over. We are one with the historic and ancient people of God.
Some Christians today will likely reply something like this "The people in the OC were not all saved, but now in the NC all God's covenant people are saved." They can say what they want to, but I believe the facts are otherwise. Folks have to ignore an awful lot of NT Scripture to make that claim or they must believe that salvation can be lost in the NC.
Question: Can branches grafted into the olive tree be cut off today?
Answer: Yes we see that in Romans 11. "Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear: For if God spared not the natural branches, take heed lest he also spare not thee." If we in the NC can be cut off from the olive tree just as those in the OC were cut off, and none who have been born again can become unsaved, then there must be some now grafted into the olive tree who are not born again. This is as it was in the OC.
Now lets look at another matter for just a moment. At the time which Paul and the other Apostles were preaching, there was only one set of Scriptures and those were the writings of what we today call the Old Testament. Some of my Christian brethren today make a gulf between the OT and NT and speak as though they are hermetically sealed from one another. However, that was not the view of the Apostles or the Church before the modern era. (Note: It was the view of a number of cults and heretical movements like Marcionism in the ancient world) That chasm that supposedly exists is not biblical and was never the position of anyone in the Church until recent history.
Let's see what we can learn from the ethnic Jews in Berea. We read:
And the brethren immediately sent away Paul and Silas by night unto Berea: who coming thither went into the synagogue of the Jews. These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so. (Acts 17:10,11)
Paul and Silas came to the Synagogue at Berea and taught the Jews there about the NT Gospel.
Question: Where did these Jews go to see if what Paul was saying about Jesus and everything else was true?
Answer: They searched the Scriptures of the Old Testament because these were the ONLY Scriptures then in existence.
I think this alone shows there must be continuity, but there is no reason to let this stand-alone. Let see what Paul said to young Timothy. Paul wrote "And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus." (II Tim 3:16)
Question: What holy Scriptures had Timothy grown up with that were able to "make thee wise unto salvation through faith which is in Christ Jesus[?]”
Answer: They were the Scriptures of the Old Testament, because these were the only Scriptures that existed when Timothy was a child. Notice that the OT was able to make young Timothy "wise unto salvation through faith which is in Christ Jesus."
Jesus Christ has always been the object of saving faith. There has never been any other object of saving faith since the beginning of the world, and this is the greatest and most important of all the continuities from OC to NC.
There is one people of God from beginning to end. We are part of that one people. There is one Scripture and it is made up of the Old and New Testaments, but these are one single Word of God. There are not two words of God for two peoples; there is but one Word for one people of God. This too is continuity.
There is a dramatic change between Old Testament and New Testament, the difference is the OT looked forward to and anticipates the coming Saviour, and the NT is better because we live in the fulfilment of the Saviours redemptive work and the outpouring of the Holy Spirit. But even with this the Bible is one book and God’s people are all one people.