Righteousness does not come by the law, but by faith. Paul uses two quotes from the Old Testament to demonstrate the point. Rules do not make people righteous, because rules do not change the heart. The path to righteousness starts with faith. Believe, speak/think on those beliefs, then do them. It is very simple, you do what you know is true and right. Paul summarizes these Old Testament passages by simply saying believe and confess. That is how faith turns into righteousness, you think or say what is true then do what is true.
Paul contrasts the Gentiles simple walk of faith, and therefore finding of righteousness, with Israel’s fixation on rules, which do not make anyone righteous. Chapter 10 is the culmination of Paul’s demolition of the competing Jewish “authorities” attack on his gospel and attempt to bring the Roman believers under their sway to follow the rules of Judaism. These “authorities” claim following rules, the law, is the path to righteousness. In this chapter, Paul culminates his argument that their claim is exactly the opposite of what is true, and as usual Paul uses Scripture (in this case the very words of Moses) to make his case.
Paul reaffirms that he cares about the Israelites’ salvation. And while there is no doubt the Jews are eagerly devoted to God, they do it by their own rules. They ignore God and make up their own way to live life.
Paul now sets forth from Moses’ writing a picture of the kind of righteousness Israel has sought, the kind that does not lead to true righteousness: righteousness based on law.
Paul uses the words of the Lawgiver Moses to demonstrate that even the law shows that true righteousness does not come by the law, but by faith.
Here, Paul restates the lesson of the previous verses, Rom 10:6-8, with a saying in the form of a chiasm.
Paul is restating to his audience of believers in Rome that there is no distinction between those Jews and Greeks who believe, that God is Lord of both, and anyone who calls upon Him gains riches and salvation.
Paul states an obvious point that we can’t believe something that we have never heard. But it is also the case that we can hear and not believe.
Paul is making it very clear that the Jewish people have heard this message of faith, but have chosen to reject it.