If you follow the law, then your circumcision has meaning. But if you break the law, then it is as if you were never circumcised. Those who are not Jews are not circumcised. But if they do what the law says, it is as if they were circumcised.
You have the written law and circumcision, but you break the law. So those who are not circumcised in their bodies, but still obey the law, will show that you are guilty.
You are not a true Jew if you are only a Jew in your physical body. True circumcision is not only on the outside of the body. A true Jew is one who is a Jew inside.
True circumcision is done in the heart. It is done by the Spirit, not by the written law. And anyone who is circumcised in the heart by the Spirit gets praise from God, not from people. (Romans 2:25-29 ERV)
Circumcision began with Abraham the patriarch. It was instituted by God with Abraham as a sign of the personal covenant between them. Later, circumcision was embedded in the Law of Moses, and became an important element of identity for Jewish males.
But the purpose of circumcision was always connected to relationship with God. It was to indicate God's seal of acceptance for those who were set apart as His people. They were to be an example to all other people in the world that one, true, living God existed.
But as with many things, the original purpose and intent of circumcision became a religious ritual rather than a sign of relationship with God. Circumcision was always intended to be more than a physical sign, as seen in Deuteronomy 10:16; 30:6; and Jeremiah 4:4.
God is always far more concerned with internal change in our hearts than outward compliance or religious obedience. The internal change is done by God's Spirit, as we surrender our heart to Him. Then, we truly become His people. ©Word-Strong_2015