Actually the scriptures say no such thing as circumcision was only a "shadow law" from the old covenant pointing to a new heart by faith from Gods' promise in the new covenant. Let's look at what the scriptures says.
for example...
ROMANS 2:28-29 [28],
FOR HE IS NOT A JEW WHICH IS ONE OUTWARDLY; NEITHER IS THAT CIRCUMCISION, WHICH IS OUTWARDS IN THE FLESH: [29], BUT
HE IS A JEW WHICH IS ONE INWARDLY; and
CIRCUMCISION IS OF THE HEART, IN THE SPIRIT, AND NOT IN THE LETTER; whose praise is not of men, but of God.
God's ISRAEL in the new covenant is not longer those born of the flesh but all those who through faith are born of the Spirit through the promises of Gods' Word...
ROMANS 9:6-8 [6],
FOR THEY ARE NOT ALL ISRAEL WHICH ARE OF ISRAEL,: [7],
NEITHER, BECAUSE THEY ARE THE SEED OF ABRAHAM, ARE THEY ALL CHILDREN: but in Isaac shall thy seed be called <Christ> [8], That is,
THEY WHICH ARE THE CHILDREN OF THE FLESH, THESE ARE NOT THE CHILDREN OF GOD:
BUT THE CHILDREN OF THE PROMISE <those who believe>
ARE COUNTED FOR THE SEED.
According to the scriptures there is no more Jewish and Gentile believers as we are now all one in Christ...
GALATIANS 3:28-29 [28],
THERE IS NEITHER JEW NOR GREEK, there is neither bond nor free, there is neither male nor female:
FOR YOU ALL ONE IN CHRIST JESUS AND IF YOU BE CHRISTS, THEN YOU ARE ABRAHAM'S SEED FOR YOU ARE ALL ONE IN CHRIST JESUS [29], and
IF YOU BE CHRISTS, THEN ARE YOU ABRAHAM'S SEED, AND HEIRS ACCORDING TO THE PROMISE.
COLOSSIANS 3:11 [11],
WHERE THERE IS NEITHER JEW NOR GREEK circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: BUT CHRIST IS ALL IN ALL.
ROMANS 10:11-13 [11], For the scripture saith, Whosoever believeth on him shall not be ashamed. [12],
FOR THERE IS NO DIFFERENCE BETWEEN JEW OR GREEK: for the same Lord over all is rich unto all that call upon him. [13],
FOR WHOSOEVER SHALL CALL UPON THE NAME OF THE LORD SHALL BE SAVED.
If you are not a part of God's ISRAEL born of the Spirit according to the scriptures you have no part in God's new covenant promise...
JEREMIAH 31:33-34 [33],
BUT THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL; After those days, says the LORD,
I WILL PUT MY LAW IN THEIR INWARD PARTS,AND WRITE IT IN THEIR HEARTS; and will be their God, and they shall be my people. [34], And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, says the LORD: for I will forgive their iniquity, and I will remember their sin no more.
Paul proclaims it here...
HEBREWS 8:10-12 [10],
BUT THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL; After those days, says the LORD,
I WILL PUT MY LAW IN THEIR INWARD PARTS, AND WRITE IT IN THEIR HEARTS; and I will be to them a God, and they shall be to me a people: [11], And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest. [12], For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.
The NEW COVENANT is for GOD'S ISRAEL which represent those who BELIEVE and FOLLOW God’s WORD. If you are not part of GOD'S ISRAEL then you are not a part of the NEW COVENANT (Hebrews 8:10-12).
............
CONCLUSION: God's ISRAEL is the name given by God to all those who BELIEVE and FOLLOW his WORD. GENTILES are now grafted in. If you are not a part of the God's ISRAEL then you have no part in the NEW COVENANT.