Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (that done in the body by the hands of men) — remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world. But now in Christ Jesus you who once were far away have been brought near through the blood of Christ.
(Eph 2:11-13 NIV)
So, as Christians, we are coheirs with the ethnic Jews — when they are not only circumcised but also walk in the footsteps of the faith that our father Abraham had before he was circumcised (Rom 4:12 NIV). Together, in Christ, both Jews and Gentiles are made one and together have access to the same father, God, through Christ (Eph 2:14,18). This, I believe, is the mystery (i.e. Eph 3:4) revealed to Paul, which he was a servant for. And the inheritance we are waiting for together, is according to the covenants of promise, given to Abraham before he was circumcised (Rom 4:10,11).
Consequently, you are no longer foreigners and aliens, but fellow citizens with God’s people and members of God’s household, built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone.
Eph 2:19-20 NIV)