What does Romans 9:21 mean?
Paul is responding to imagined questions from readers of his letter. He has been making the case that God can and does give mercy to whomever He wishes. He does this based on nothing more than His own purposes and glory (Romans 9:15–16). Nobody "deserves" grace and mercy, by definition (Romans 3:10; 3:23). So there's nothing unfair or unjust about God granting mercy to some, and none to others. Nor is there anything wrong with God purposefully using His creations to demonstrate His glory (Romans 9:17–18).Paul's last example was that of Pharaoh, in the Exodus, who experienced a God-hardened heart which contributed to God raining more plagues down on Egypt. Paul imagines his readers asking, in essence, "How could God blame Pharaoh for being resistant if Pharaoh had no choice in the matter?"
In the prior verse, Paul turned the tables: Who are we, as mere humans, to question God? More to the point, how can we, as created things, question our Maker?
Following that idea, Paul asks if a potter has the right to make whatever he wants from the clay. Is he allowed to make from the same lump one pot for "honorable" things, such as holding flowers or valuables, and another pot for "dishonorable" things, such as a toilet or waste bin? Of course, the potter has an absolute right to do whatever he wants with the clay. And God has an absolute right to do whatever He wants with man.
Paul's case that God can do as He likes corrects our usual thinking about God and us. The Maker gets to decide what He will make and what He will do with it. The thing which has been made has no say in that, morally or otherwise, no matter how loudly we might complain.
Paul's response is harsh, but it's absolutely beyond argument. That combination of truth and humility is why his point is hard for us to take. Paul will modify this point slightly in the verses to follow, emphasizing God's love and mercy to some, but not to all. His larger point will be that though God is loving, kind, and just, He does not owe anything to any human person. Everything He gives to us is a gift of grace.
This, in fact, is a key point in appreciating the gospel. If God owed some people, or any people His mercy, then it would remove the element of grace (Romans 4:2–5; 11:6). The reason Scripture speaks of God's love in such amazing terms (John 3:16) is because that love is unearned and undeserved. These are two inseparable sides of the same coin: God has the sovereign right to do anything He wants with His own creation, and yet He chooses to show some of us profound mercy through salvation.
