What does Romans 3:30 mean?
This completes a thought begun in the previous verse. Paul has just written that God is the God of both the Jews and the Gentiles. Many Jewish people throughout Israel's history might have objected to that statement. In their minds, God was Israel's God. The Gentile nations worshiped a collection of other gods and idols, so they could not claim the One True God as their own.Paul's point however is that "God is one." In other words, there are no other gods. Gentiles will not stand before the judgment seat of Baal, or Zeus, or any other false god after they die. Those gods literally do not exist. Rather, all people, Jews and Gentiles alike, are accountable to the one, true God for their sin and for their faith.
In both cases, the only hope to be declared righteous by God, to be justified, is faith in Christ. When it comes to that judgment, God will justify the circumcised, meaning Jewish people, and the uncircumcised, meaning everyone else, through faith in Christ. The people of Israel have some advantage in their special relationship to God (Romans 3:1–2), but they will be held accountable to the exact same standards as anyone else (Romans 3:9–10).