Romans 4:11

The sign of circumcision — i.e., circumcision as a sign. The expression is an instance of what is known in Greek as the “genitive of apposition,” but it is common in English. Thus we speak of the City of London, the County of Kent.

Abraham is the father (1) of faithful uncircumcised — he himself being so — and (2) of circumcised, but only of faithful circumcised.

A seal of the righteousness ... — The Apostle here puts forth his view of the real import of circumcision. It was not (as so many of his contemporaries supposed) the cause or condition of Israel’s privileges so much as the sign or ratification of them. It ratified a state of things already existing when it was instituted. Hence, to those who inherited that state of things (justification by faith) the want of circumcision was no bar.