So it depends not on human will or exertion, but on God who shows mercy.
For the scripture says to Pharaoh, "I have raised you up for the very purpose of showing my power in you, so that my name may be proclaimed in all the earth."
So then he has mercy on whomever he chooses, and he hardens the heart of whomever he chooses.
You will say to me then, "Why then does he still find fault? For who can resist his will?"
But who indeed are you, a human being, to argue with God? Will what is molded say to the one who molds it, "Why have you made me like this?"
Has the potter no right over the clay, to make out of the same lump one object for special use and another for ordinary use?
What if God, desiring to show his wrath and to make known his power, has endured with much patience the objects of wrath that are made for destruction;
and what if he has done so in order to make known the riches of his glory for the objects of mercy, which he has prepared beforehand for glory—
including us whom he has called, not from the Jews only but also from the Gentiles?
As indeed he says in Hosea, "Those who were not my people I will call "my people,' and her who was not beloved I will call "beloved.' "
"And in the very place where it was said to them, "You are not my people,' there they shall be called children of the living God."
And Isaiah cries out concerning Israel, "Though the number of the children of Israel were like the sand of the sea, only a remnant of them will be saved;
for the Lord will execute his sentence on the earth quickly and decisively."
And as Isaiah predicted, "If the Lord of hosts had not left survivors to us, we would have fared like Sodom and been made like Gomorrah."
What then are we to say? Gentiles, who did not strive for righteousness, have attained it, that is, righteousness through faith;
but Israel, who did strive for the righteousness that is based on the law, did not succeed in fulfilling that law.
Why not? Because they did not strive for it on the basis of faith, but as if it were based on works. They have stumbled over the stumbling stone,
as it is written, "See, I am laying in Zion a stone that will make people stumble, a rock that will make them fall, and whoever believes in him will not be put to shame."