Isaiah 29:16

If a man seems more comely to look upon than clay, this difference was not produced by a change of nature but by the wisdom of the craftsman. Why? Because you are no different from the clay. If you refuse to believe this, let the coffins and the cinerary urn convince you. And you will know that this is the truth if you have gone to visit the tombs of your forebearers. Therefore there is no difference between the clay and the potter.

God comes down to the level of sinful men and women; the good Lord speaks with his rebellious servants; the holy one calls those who are impure to forgiveness. Humanity created out of mud addresses its Fashioner with familiarity; dust converses with its Maker. Let us, therefore, show awe when we sinners stand in the presence of this Majesty and speak. Even though we are so impure in our deeds, he draws us close to the sight of himself in the spirit; let us therefore repeat with trembling the words of the blessed prophet Isaiah: "Woe is me, for I am dazed: I am a man of unclean lips, yet my eyes have beheld the King, the Lord Almighty."

Scripture says to Pharaoh, "To this purpose have I raised you that I may show my power in you; and that my name may be declared throughout all the earth." Then, making a conclusion to both passages, he says, "Therefore he has mercy on whom he will and whom he will he hardens." Obviously he treats neither of these with injustice but both with mercy and truth; in spite of that there is an uprising of insolent weakness on the part of those who attempt to comprehend the unsearchable depth of the judgment of God according to the interpretations of the human heart. The apostle refutes this view when he says, "You will say therefore to me: Why does he then find fault? For who resists his will?" Let us imagine this as said to us. What other answer should we make than the one he made? If such ideas disturb us also because we, too, are human, we all have need to listen to the apostle saying, "O man, who are you that replies against God? Shall the thing formed say to him that formed it: Why have you made me thus? Or has not the potter power over the clay, of the same lump to make one vessel unto honor, another unto dishonor?" If this lump of clay were of such indifferent value that it deserved nothing good any more than it deserved anything evil, there would be reason to see injustice in making of it a vessel unto dishonor. But when, through the free will of the first man alone, condemnation extended to the whole lump of clay, undoubtedly if vessels are made of it unto honor, it is not a question of justice not forestalling grace, but of God's mercy. If, however, vessels are made of it unto dishonor, it is to be attributed to the judgment of God, not to his injustice—far be from us the thought that there could be any such with God! Whoever is wise in this matter with the Catholic church does not argue against grace in favor of merit, but he sings mercy and judgment to the Lord, that he may not ungratefully deny his mercy or unjustly upbraid his judgment.