How is Abraham the father of uncircumcised believers?

Abraham received the sign of circumcision as a seal of the righteousness he already had by faith while uncircumcised. Therefore he is the father of all uncircumcised believers, so that righteousness might be imputed to them also, tying Abraham to us.

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, Assyrian by birth, as a non-Jew before the nation was on the scene. God dealt with him while he was still in idolatry, and by faith Abraham left, not after circumcision was implemented, but before. In verse 11 he received the sign of circumcision as a seal of the righteousness of the faith he had while yet uncircumcised, so he came into justification before circumcision was mentioned to him. Thus he is the father of all them that believe, though they be not circumcised, that righteousness might be imputed unto them also. Les teaches this ties Abraham to us, because we are not part of the circumcision covenant but are uncircumcised in Scripture’s relationships.

Romans 4:11

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:

Was Abraham justified before or after he was circumcised?

Abraham was justified before he was circumcised. Scripture says he received the sign of circumcision as a seal of the righteousness of the faith which he had while still uncircumcised. He came into this justification position before circumcision had even been mentioned to him, while still uncircumcised.