“For he saith to Moses, I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.” Romans 9:15 (KJV 1900)
“Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.” Romans 9:18 (KJV 1900)
“Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour?” Romans 9:21 (KJV 1900)
“What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction: And that he might make known the riches of his glory on the vessels of mercy, which he had afore prepared unto glory, Even us, whom he hath called, not of the Jews only, but also of the Gentiles?” Romans 9:22–24 (KJV 1900)
Jeremiah ch 18, the potter and clay chapter, explains what Paul was writing in Romans ch 9, and the Calvinist interpretation is absolutely wrong.
The potter and clay, and Jacob and Esau, is about NATIONS not individuals.
As Rebecca was told in Genesis 25:23 concerning her pregnancy: two nations are in your womb (Edom came from Esau, and Israel came from Jacob)
And Israel, the nation from Jacob is the clay on the potters wheel, not any one person.
The Potter and the Clay.
Jer 18:1 The word which came to Jeremiah from the LORD, saying,
Jer 18:2 Arise, and go down to the potter's house, and there I will cause thee to hear my words.
Jer 18:3 Then I went down to the potter's house, and, behold, he wrought a work on the wheels.
Jer 18:4 And the vessel that he made of clay was marred in the hand of the potter: so he made it again another vessel, as seemed good to the potter to make it.
Jer 18:5 Then the word of the LORD came to me, saying,
Jer 18:6 O house of ISRAEL , cannot I do with you as this potter? saith the LORD. Behold, as the clay is in the potter's hand, so are ye in mine hand, O house of Israel.
We also find in Jeremiah 18 that when the potter speaks blessing over any NATION and they turn evil, God takes back his blessing and punishes that nation, and also when the potter considers a nation a vessel fit for destruction and they repent, He changes His mind about punishing them.
No nation is predestined to destruction.
Jer 18:7 At what instant I shall speak concerning a NATION, and concerning a kingdom, to pluck up, and to pull down, and to DESTROY it;
Jer 18:8 If that NATION, against whom I have pronounced, turn from their evil, I will REPENT of the evil that I thought to do unto them.
Jer 18:9 And at what instant I shall speak concerning a NATION, and concerning a kingdom, to build and to plant it;
Jer 18:10 If it do EVIL in my sight, that it obey not my voice, then I will REPENT of the good, wherewith I said I would benefit them.
This is the opposite of the reformed doctrine predestination narrative. The fate of the nations is dependent on what they do, not on being predestined to be vessels of wrath, fitted for destruction, and the Romans 9 potter and clay passage is not about predestination of individuals to hell, or to salvation.
God will have mercy on whom He will - and His will is He has mercy whenever there is repentance, and takes back His mercy, if they turn to doing evil.
That God changes His mind based on what a nation does (repentance) or doesn’t do right (turns to evil) absolutely wrecks reformed dogma regarding God being immutable.