The following passage really makes up the heart of Paul's Epistle to the Ephesians. Here he reveals a great mystery which was hidden in previous ages:
"Therefore remember that at one time you Gentiles in the flesh, called "the uncircumcision" by what is called the circumcision, which is made in the flesh by hands— 12 remember that you were at that time separated from Christ, alienated from the commonwealth of Israel and strangers to the covenants of promise, having no hope and without God in the world. 13 But now in Christ Jesus you who once were far off have been brought near by the blood of Christ ... So then you are no longer strangers and aliens, but you are fellow citizens with the saints and members of the household of God, 20 built on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone, 21 in whom the whole structure, being joined together, grows into a holy temple in the Lord."
Notice in this passage that Paul speaks to Gentiles as having been previously separate and alienated from Israel and the covenants of promise, but in Christ, Gentiles have also become citizens of Israel. The phrase "brought near" was their modern day parlance for Jewish proselytes. According to this passage we Gentiles now partake of the same promises and are no longer strangers to the commonwealth of Israel, but citizens of it. Notice the clear reference to Jesus Christ as the true Israel, and this includes are all who are joined to His body. Let’s have a closer look: Verse 12 "alienated from the commonwealth of Israel" Paul now joins Gentiles to (vr. 19) "you are no longer strangers and aliens". No longer aliens to what? No longer aliens to the commonwealth of Israel. That means that Gentiles who are in Christ are now "citizens" (v. 19) of Israel built as a house with Christ as the chief cornerstone. In other words, Jesus Christ is the True Israel of God (its fulfillment and foundation) as are all who are joined in union to Him. To say it another way, both OT and NT saints who are in union with Christ are now citizens of Israel. Likewise According to Ephesians 3: 4-6, God made known a mystery to Paul "...the mystery of Christ, which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit. This mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel."Partakers of what promise? The promises given to Israel to Abraham of course. Did not God promise to Abraham that through him all the nations would be blessed? And since the Paul elsewhere asserts that the gospel was preached to Abraham beforehand (Gal 3:8), the OT and NT saints were both saved by the same grace in Christ and are members of the same body .... partakers of the same covenant promises. The difference is simply (if you think about it organically) that one was a mere seedling or imature branch and the other a fully mature fruit-bearning tree, but both are part of the same tree. The OT saints saw Christ from a distance in promises and shadows, yet in God's economy those regenerate were, even then, united to Christ, part of the same body and saved by the same blood ... the blood which the signposts of the temple sacrifices pointed to.
“And all these, though commended through their faith, did not receive what was promised, since God had provided something better for us, that apart from us they should not be made perfect.” (Heb 11: 39, 40)
Just as we can never separate the law from the lawgiver, we likewise cannot separate the benefits from the benefactor. Many in modern day evangelicalism have wrongly divided the people of God, evewn while Paul here was at pains to show them both in union with Christ. Since Paul stressed the importance of this lets look afresh at the Scripture beyond our traditions and errors regarding this issue. The Text of Scripture is not Israelocentric but Christocentric. Jesus himself bore witness to this: "You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me." (John 5:39)