What was the function of circumcision in Romans 4:11?
Scripture presents circumcision as a sign and seal of the righteousness of faith Abraham already possessed while still uncircumcised. It did not produce justification; it confirmed the righteousness imputed by faith before circumcision, so Abraham could be father of all who believe, including the uncircumcised.
Les explains that circumcision was given to Abraham after he had already believed and been justified. The context notes that for the first 2,000 years there had been no hint of circumcision or the Mosaic Law. Abraham came out of Ur of the Chaldees as a non-Jew, and God dealt with him while he was still in idolatry; by faith he left, not after circumcision was implemented but before. Therefore, circumcision was the sign and seal of the righteousness of the faith he had while yet uncircumcised. It marked that he came into justification before circumcision was even mentioned to him. This fits the purpose that he might be the father of all them that believe, though they be not circumcised, that righteousness might be imputed unto them also. Les ties Abraham to us, the uncircumcised, showing we are not part of the circumcision covenant.
And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also: