A go-to verse for Calvinists, and a problem verse for non-Calvinists, is Romans 9:22. The verse clearly exemplifies the premises of Sovereign Election and Definite Atonement in the plain reading of the verse.
“What if God, desiring to show his wrath and to make known his power, has endured with much patience vessels of wrath prepared for destruction,”Romans 9:22, ESV
Vessels of wrath prepared for destruction. It is plain and simple. Not everyone is elect to salvation. Some, in fact, many, will be left behind in their own rebellion against God.
Non-Calvinists try many ways to explain away this verse but none of them are adequate. Of course, there is also burden on the Calvinist to provide evidence in the rest of Scripture for their position on the passage as well. Does this evidence exist? The answer is yes, it does.
First, the passage itself gives its own citations for this position. Malachi 1:2-3, Exodus 9:16 and Exodus 33:19. The pictures of Esau vs. Jacob and Moses vs. Pharaoh are vivid with relation to election. God has made the choices of those whom He will use for His purposes and those, in the case of Pharaoh, who will be used for His purposes and destroyed in the process.
But the second thing that should be pointed out is that we also see this principle in the conquest of Canaan. The Old Testament makes very clear that Israel was chosen, others were not and that they were meant for destruction. Consider Deuteronomy 7:2:
“and when the Lord your God gives them over to you, and you defeat them, then you must devote them to complete destruction. You shall make no covenant with them and show no mercy to them.”Deuteronomy 7:2, ESV
Israel was to devote these people, without discrimination, to destruction. These people were not given a chance to hear about Yahweh. Now, the argument will be made that they would have known about the God of Israel but that is not within the text. They were to be destroyed. That was their purpose. Men, women, children, animals, possessions. They were all to be destroyed. But it goes deeper than that.
To make the point, we see this idea of being devoted to destruction in many Old Testament Passages (Ex. 22:20, Lev 27:29, Num 21:2-3, Deut 2:34; 3:6; 7:2, 26; 13:15; 20:17; Josh 2:10; 6:17-18, 21; 7:12; 10:1 to name a few). The word used is ḥā·rǎm and it is used to say destroyed, utterly destroyed, as an offering to the Lord.
That is exactly what we see in Romans 9:22, vessels of wrath prepared for destruction and then verse 23 says that this destruction is to make known the riches of his glory.
It is understandable that this is a hard pill to swallow but it is truth. Some people were never going to be saved. That does not mean they are not at fault. They are still sinners. But God was never going to save them. He has a specific people that He has chosen to save for his glory.