That is why all turns upon faith; it is to make the promise a matter of favour, to make it secure for all the offspring, not simply for those who are adherents of the Law but also for those who share the faith of Abraham — of Abraham who is the father of us all
He only got circumcision as a sign or seal of the righteousness which belonged to his faith as an uncircumcised man. The object of this was to make him the father of all who believe as uncircumcised persons and thus have righteousness counted to them,