But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
Romans 2:29
It represented the new creations in Christ. It is the circumcision of the heart, that is, salvation. The cutting away of the old, and the display of the new. The law was fufilled in us through Christ. It kept his people sanctified, or "seperated", so that they were marked to show the coming of the Christ.