Paul has just shown that Jacob was chosen over Esau before either had done anything. Now the objection surfaces that anyone reading along has probably felt: 14"Is there injustice on God's part?" Paul answers with who God has revealed himself to be. 15"I will have mercy on whom I have mercy," God told Moses, and Paul lets it stand as the answer. Mercy was never a wage owed to anyone. 16"It depends not on human will or exertion, but on God, who has mercy."
Then Pharaoh becomes the example: God tells Pharaoh, 17"For this very purpose I have raised you up." It reads harshly until you recall Pharaoh's history in Exodus, where his hardening is described as his own several times before it is described as God's (Exodus 8:15, 32; 9:12). God let an already-rebellious king run his hardened will to its full and public length and used even that resistance to make his power known.
The objector pushes again: 19"Why does he still find fault?" Paul turns the question back on the questioner. 20"Who are you, O man, to answer back to God?" A potter takes ordinary clay, common enough that everyone in Paul's audience had shaped or used it, and makes from one lump one vessel for honorable use and another for less honorable. The clay was never in a position to negotiate its own shape, and Paul's whole reply is the potter's right over the clay. A creature who demands an accounting from its Creator has misunderstood which of them is asking the question. Paul says so in the same breath in which he insists that God has borne with patience even those he might have destroyed at once.
Paul phrases the two halves differently. He speaks of 22"vessels of wrath prepared for destruction" alongside 23"vessels of mercy, which he has prepared beforehand for glory." Mercy, he says plainly, God himself prepared beforehand. Wrath he describes only as prepared, without pointing to who did the preparing. Paul is more eager to say where mercy came from than to explain where wrath came from. The riches of God's glory are the point of the passage, made known to us whom he has called 24"not from the Jews only but also from the Gentiles."
That is where it lands. Paul quotes Hosea, spoken over rejected, exiled Israel: 25"Those who were not my people I will call 'my people.'" If God could call his own estranged people beloved again, he could call outsiders who had never belonged to him by the same word. And Isaiah, warning that only a remnant would be saved, says that had the Lord not left offspring, 29"we would have been like Sodom." Grace was the only reason anyone, Jew or Gentile, was left standing.
Ask whom you have resented God for showing mercy to, and remember what you were before he showed it to you.
Prayer
Father, you are the potter and we are the clay, and we do not always like being told so plainly. Forgive us the moments we have resented your mercy toward someone we thought undeserving, when we never deserved it either. Thank you for calling a people from the Jews and the Gentiles, called beloved. Shape us into the vessel you have prepared us to be. In Jesus' name, amen.