I've lost count of the number of times vekky & I have answered this one, so by way of (a very brief) reply, let me put a few questions to you instead of going over old ground again.
According to the NT, who are the true circumcision; the seed/children/heirs of the promise; the sons/ seed/offspring of Abraham; the children of the free woman - ie Sarah; the tabernacle of David; the temple of God; the real (heavenly) Jerusalem; a chosen race; a royal priesthood and a holy nation? What is a real/true Jew and who/what is the Israel of God in Gal. 6:16? And by way of contrast, what was said to (and about) those who relied on their physical ancestry as a guarantee of their standing before God?
Now go, seek out all these phrases (and quite possibly a few more besides that I've left out) in your Bible, and tell us what you find. You will then have answered your own question, and done so without the aid of 'the writings of men'.