What is interesting about the Passover is that, as anyone familiar with Scripture knows, it celebrates the final and most terrible plague God visited on Egypt in response to the God-hardened heart of Pharaoh preventing him from letting the Hebrews go. The first born of the Egyptians were struck down and the Hebrews were spared but they weren't spared because they were Jews. They were spared because of the blood of the Passover lamb on their door.
For I will pass through the land of Egypt that night, and I will strike all the firstborn in the land of Egypt, both man and beast; and on all the gods of Egypt I will execute judgments: I am the LORD. The blood shall be a sign for you, on the houses where you are. And when I see the blood, I will pass over you, and no plague will befall you to destroy you, when I strike the land of Egypt. (Exodus 12:12-13)
Then Moses called all the elders of Israel and said to them, "Go and select lambs for yourselves according to your clans, and kill the Passover lamb. Take a bunch of hyssop and dip it in the blood that is in the basin, and touch the lintel and the two doorposts with the blood that is in the basin. None of you shall go out of the door of his house until the morning. For the LORD will pass through to strike the Egyptians, and when he sees the blood on the lintel and on the two doorposts, the LORD will pass over the door and will not allow the destroyer to enter your houses to strike you. (Exodus 12:21-23)
As an aside it is worth pointing out that Moses was quite clear. It was not some impersonal force that swept through and slew the first born. God Himself told Moses "I will pass through the land of Egypt" and "I will strike all the firstborn". In spite of our tendency to portray God the Father as a kindly and perhaps doddering old man and Jesus as His groovy proto-hippie son, it was God Himself who slew the firstborn of Egypt, the eldest child of the Pharaoh and the prisoner, the great and the small, without partiality. Only the blood of the Passover lamb caused His wrath to be stayed.
My point here is not a retelling of the Passover story but to apply the Passover to the idea of sovereign divine election. For those who deny the sovereign election of a specific, elect people by God for salvation, one of the common objections is that they think God is somehow capriciously dividing people into two groups, those He saves and those He does not save. It is sort of like they see God picking teams for kickball except that He picks for both teams. Person A gets called out from the mass of humanity for Team Elect and then Person B gets called out for Team Reprobate.
What the Bible teaches and what Reformed theology teaches is quite different. All men start out on Team Reprobate and God in His infinite sovereign mercy elects some to be saved out of that group. Ironically a lot of people quote John 3:16 as if that somehow proves that God doesn't take an active hand in electing people but just a couple of verses later Jesus Himself gives the first part of the electing formula and the first letter in the Calvinist acrostic TULIP, the "T" for "Total Depravity":
Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God. (John 3:18)
Jesus doesn't come to condemn the world (John 3:17) because the world is already completely condemned. Reprobation or condemnation is the natural state of every single human being. All have sinned and all have fallen short and therefore all stand condemned and in need of a Savior (Romans 3:23). Humans are not and never have been "neutral". You are either justified by being in Christ or you are remain where you started, condemned and outside of Christ. There is no middle ground, no grace period, no purgatory. The Reformed confessions confirm this in their discussion of God's sovereign decree:
By the decree of God, for the manifestation of his glory, some men and angels are predestinated, or foreordained to eternal life through Jesus Christ, to the praise of his glorious grace; others being left to act in their sin to their just condemnation, to the praise of his glorious justice. Chapter 3, 1689 Baptist Confession
V. Those of mankind that are predestinated unto life, God, before the foundation of the world was laid, according to His eternal and immutable purpose, and the secret counsel and good pleasure of His will, has chosen, in Christ, unto everlasting glory, out of His mere free grace and love, without any foresight of faith, or good works, or perseverance in either of them, or any other thing in the creature, as conditions, or causes moving Him thereunto; and all to the praise of His glorious grace.
VII. The rest of mankind God was pleased, according to the unsearchable counsel of His own will, whereby He extends or withholds mercy, as He pleases, for the glory of His sovereign power over His creatures, to pass by; and to ordain them to dishonor and wrath for their sin, to the praise of His glorious justice. Westminster Confession of Faith, Chapter 3The WCF even uses the terminology of "passing by", an obvious allusion to the Passover in Egypt.
This is not parsing the number of angels that can dance on the head of a pin. These are substantive and critical and foundational truths. If all men stand condemned in their natural unregenerate state, as the Bible teaches, and if these men are spiritually dead in their sins and tresspasses and children of wrath (Ephesians 2:1-5) and enemies of God, then it follows that rather than dividing men out of a neutral position into "elect" and "reprobate", God instead chooses from the reprobate some to be elect and saved, and those He chooses have the wrath of God "pass over" them by virtue of the blood of the Lamb, Jesus Christ. All humanity, every single person born, alive and yet to be born, stands under judgment. Without exception. Only by the sovereign election of God are any redeemed.
I can respect that some people, most Christian in fact, don't agree with my conclusions. What I can't respect is when people either willfully misrepresent what I and others like me are saying or when people don't take the time to understand what they are rejecting.
If you don't understand sovereign election, I don't think you can really understand the Passover and if you don't understand the Passover, how can you really understand the cross?
What then? Are we Jews any better off? No, not at all. For we have already charged that all, both Jews and Greeks, are under sin, as it is written: "None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside; together they have become worthless; no one does good, not even one." (Romans 3:9-12)