Albert Barnes Commentary Romans 3:30

"if so be that God is one, and he shall justify the circumcision by faith, and the uncircumcision through faith." — Romans 3:30 (ASV)

It is one God. The same God; there is only one, and his plan is equally suited to Jews and Gentiles.

The circumcision. Those who are circumcised—the Jews.

The uncircumcision. Gentiles; all who were not Jews.

By faith—through faith. There is no difference in the meaning of these expressions. Both denote that faith is the instrumental cause of justification, or acceptance with God.