Even as Abraham believed God, and it was accounted to him for righteousness. Abraham believed God - This is quoted from Genesis 15:6 (note); and St. Paul produces it, Romans 4:3-5 (note). Abraham, while even uncircumcised, believed in God, and his faith was reckoned to him for justification; and Abraham is called the father of the faithful, or, of believers. If, then, he was justified without the deeds of the law, he was justified by faith; and if he was justified by faith, long before the law was given then the law is not necessary to salvation.
It is remarkable that the Jews themselves maintained that Abraham was saved by faith. Mehilta, in Yalcut Simeoni, page 1, fol. 69, makes this assertion: "It is evident that Abraham could not obtain an inheritance either in this world or in the world to come, but by faith."