As we find in Genesis 17, circumcision was the sign of God's covenant with Abraham, just as the rainbow was the sign of God's covenant with Noah. Circumcision itself did nothing inward for the soul. It was an outward sign of God's covenant pertaining to outward blessing. The sign was consequent on God’s unconditional promises made to Abraham and his descendants. Those promises will be fulfilled ultimately by Christ, because God is faithful. The sign of circumcision was not given to Abraham as a legal thing, but rather how Abraham might respond to the grace of God.1 Many years later, when the law was given with its conditional promises, it included circumcision as part of the ceremonial law. This linked circumcision with the moral law; "for I testify again to every man that is circumcised, that he is a debtor to do the whole law" (Gal. 5:3). Israel, in breaking the law, disqualified themselves from any outward blessing, and so circumcision became of no profit, and has no place in Christianity.
Quite strongly in Galatians, Paul shows that circumcision for religious purposes2 is expressly prohibited, because sets aside the work of Christ; "that if ye are circumcised, Christ shall profit you nothing" (Gal. 5:2). Even for a Jew, God never intended circumcision to be rested in without faith. In Romans 2, Paul addresses the issue of Jews who clung to circumcision as an irrevocable pledge of God’s blessing on them regardless of obedience to the law, and believed that it was impossible that God would judge them. The Jews were mistakenly trusting in the rite of circumcision, which has to do with temporal blessing, and were imagining that it secured their eternal blessing. Paul shows that for a Jew, the outward sign of circumcision was not all God was looking for; "For he is not a Jew who is one outwardly, neither that circumcision which is outward in flesh; but he is a Jew who is so inwardly; and circumcision, of the heart, in spirit, not in letter; whose praise is not of men, but of God" (Rom. 2:28-29).