Was Abraham justified before circumcision was ever mentioned?
Abraham was justified by faith while still uncircumcised, before circumcision had even been mentioned to him. Scripture states he received circumcision later as a sign and seal of the righteousness of the faith he already possessed. His justification therefore did not come by virtue of circumcision or the covenant relationship.
Les explains that for the first 2,000 years there was no hint of circumcision or the Mosaic Law. Abraham came out of Ur of the Chaldees as a non-Jew, Assyrian by birth, while the nation was not yet on the scene. God dealt with him in the midst of idolatry and said, "Leave and go to a place that I will show you." By faith Abraham left—not after circumcision was implemented, but before. Verse 11 says he received the sign of circumcision as a seal of the righteousness of the faith he had while yet uncircumcised. Thus he entered the justification position before circumcision had even been mentioned to him. Les ties this to us: we are uncircumcised, not part of the circumcision covenant, so Abraham is the father of all who believe, even the uncircumcised, that righteousness might be imputed to them also.
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: