What then are we to say? Is there injustice on the part of God? Of course not! For he says to Moses: "I will show mercy to whom I will, I will take pity on whom I will." So it depends not upon a person's will or exertion, but upon God, who shows mercy. For the scripture says to Pharaoh, "This is why I have raised you up, to show my power through you that my name may be proclaimed throughout the earth." Consequently, he has mercy upon whom he wills, and he hardens whom he wills. You will say to me then, "Why (then) does he still find fault? For who can oppose his will?" But who indeed are you, a human being, to talk back to God? Will what is made say to its maker, "Why have you created me so?" Or does not the potter have a right over the clay, to make out of the same lump one vessel for a noble purpose and another for an ignoble one?
(Romans 9:14-21 NAB)