Throughout the Old Testament, circumcision was the method by which Jews were brought into the family of God. Throughout the New Testament, believer’s baptism, was the method by which men and women were brought into the family of God.
As I recently read through a portion of St. Paul’s letter to the Romans (chapter 2), I substituted the word “Christian” for Jew, and ‘baptism’ for circumcision. It was not difficult to extrapolate the important point:
“But if you bear the name “Jew” and rely upon the Law and
boast in God, 18 and know His will and approve the things that are essential, being instructed out of the Law, 19 and are confident that you yourself are a guide to the blind, a light to those who are in darkness, 20 a corrector of the foolish, a teacher of the immature, having in the Law the embodiment of knowledge and of the truth, 21 you, therefore, who teach another, do you not teach yourself? You who preach that one shall not steal, do you steal?
22 "You who say that one should not commit adultery, do you commit adultery? You who abhor idols, do you rob temples? 23 You who boast in the Law, through your breaking the Law, do you dishonor God? 24 For “the name of God is blasphemed among the Gentiles because of you; Just it is written.”
“For indeed circumcision is of value if you practice the Law; but if you are a transgressor of the Law, your circumcision has become uncircumcision. 26 So if the uncircumcised man keeps the requirements of the Law, will not his uncircumcision be regarded as circumcision? 27 And he who is physically uncircumcised, if he keeps the Law, will he not judge you who though having the letter of the Law and circumcision are a transgressor of the Law? 28 For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh"
29 "But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter; and his praise is not from men, but from God.”