30 Seeing [epeiper] it is one [heis] God [theos], which [hos] shall justify [dikaioo] the
circumcision [peritome] by [ek] faith [pistis], and [kai] uncircumcision [akrobustia]
through [dia] faith [pistis]. KJV-Interlinear
God is one—who will justify the circumcised by faith and the uncircumcised
through faith. ESV
One God. And that means one policy, one faith, one salvation.
The Bible only recognizes two categories of people in this world, the Jews and the Gentiles. Circumcision often served to likewise distinguish the difference between these two categories.
Today, circumcision is a mere medical practice which applies to many groups.
The Jews, since they were the custodians of the scriptures, and thus set apart from all other peoples. And the gentiles who are comprised of everyone else.
This classification laid down the framework for identifying those who belonged to God and those who did not. The gentiles were often times referred to as foreigners or aliens or strangers, to describe their lack of citizenship or relationship in Gods kingdom, and in Gods family.
You are either in Gods family and kingdom, or you are not. There is no third category of people.
But in any case, all peoples were treated the same. Admittance is by means of faith.
To the Jews, who by the way, were not immediately or automatically born into Gods family just because of their birth, but they had to believe in the savior, which is faith. They had custody of the scriptures and knew or should have known that works as identified in the scriptures, was a path to eternal death, not to eternal life. So, by faith they would be saved.
The gentiles, on the other hand, did not have the scriptures, so works was never an issue, but the gospel was, and upon hearing the gospel, regardless of its source, then salvation was and is accomplished through faith.
The by faith and through faith designations only indicate from where the information came, but faith is the same in either case.