What does Romans 9:24 mean?

Paul has been making the point that God, as the sovereign Creator (Romans 9:20–21), can show mercy to whomever He wishes based only on His own purposes. He does not owe us, His creatures, anything at all. We have universally earned His wrath with our sinfulness (Romans 3:10; 3:23). If He chooses to show mercy, it is not unfair of Him to grant that grace only to some of us. Nobody deserves it; not one person has the right to say, "you ought to have been merciful to me, too."

The previous verse described those to whom God will make known the riches of His glory—in Christ—as "vessels of mercy" which He has prepared beforehand for glory. Now Paul begins to bring his point home and to return to the subject with which he began this chapter.

He writes that these vessels of mercy are "us." In this context, that means all those God has called out, in Christ, from both the Jewish people and from the Gentiles. What does it mean that we are "called out?" It means we're one of these whom God prepared for mercy. It means our national identities are not the most important thing God considers about us. When we are saved, regardless of our heritage, we become God's people, as Paul will write in the following verse.