That it may not be thought that God is variable in the action of justifying sinners, but that it might be known that he is one, i.e. unchangeable, he shows, that both the circumcised Jews and uncircumcised Gentiles are justified by the same God in Christ, and by the same way and manner, viz. by and through faith, with no more difference than there is betwixt these two phrases, (by faith and through faith), which cannot be distinguished the one from the other.
Related Commentaries of Romans 3:30
Romans 3:30
30 Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.