Romans 3:29-31 — Is He the God of the Jews only? is He not also of the Gentiles? Yes, of the Gentiles also:
Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.
Do we then make void the law through faith? God forbid: yea, we establish the law.
There is one God (a foundational truth of the Jews), therefore, He is God to Jews and Gentiles.
Faith doesn't void the Law, it completes it and fulfills it.
By faith = out of faith, as opposed to "out of law"
Through faith = by means of, with no Law to be saved out of.
The Jews were justified by faith, by way of works, whereas Gentiles are justified directly by way of faith.
Christ satisfied the Law, therefore He established justification by the Laws' demands (verse 31).