Reference

Romans 4:1-25
"The Father of Us All"

Having contended that justification is a gift of grace received through faith, Paul points to the ancestor of the Jews, Abraham, to demonstrate this truth.  Contrary to what some believed, Abraham was credited as righteous apart from circumcision and from works of the Law, but rather on the basis of faith.  This reality highlights the fact that subsequently he is the father of all who share in his faith, both Jew and Gentile, united as one people of God at the foot of the cross.