What does Romans 4:12 mean?
Paul is showing that Abraham's faith, and God's declaration that he was righteous because of it, caused him to become the father of all believers in God, both Gentile and Jewish. In the previous verse, Paul showed that Abraham believed God and was declared righteous long before he was circumcised. This made Abraham a spiritual father to everyone who believes God without being circumcised, referring to all non-Jewish people, whether circumcised for other reasons or not.Now Paul shows that Abraham was also the father of circumcised people, as well. However, in this case Paul is not referring to all of them. Abraham is, of course, physically the father of all the Jewish people. He is their primary ancestor. They are his descendants. Paul, however, qualifies this second group of the children of Abraham.
He describes them as, yes, circumcised and Jewish, but also as those who walk in his footsteps by having the same faith in God Abraham did before he was circumcised. In other words, Abraham became the spiritual father both of the believing non-Jews and the believing Jews. Paul's point here is crucial: even under circumcision, faith is what truly separates those who are in God's family from those who are apart from it. Abraham set the example for all who would follow in faith.