The instructions for the Passover in Egypt give us a foundation for understanding this feast:
As this passage shows, the Passover lamb did much more than just provide blood - it was a distinctive meal. God begins with instructions to ensure that every person would have enough, but also that it would not be wasted. He continues with specific details, including when it should be eaten, how it should be prepared, what should be eaten with it, what should be done with the remains, and even how the Israelites should be dressed. The bulk of God's instructions concern the specially prepared lamb they were to eat. The repeated emphasis in both Old and New Testaments is on the eating of the Passover (Exodus 12:43, 48; 34:25; Numbers 9:11; II Chronicles 30:18; Ezra 6:21; Matthew 26:17, 26; Mark 14:12, 14, 22; Luke 22:8, 11, 15, 19; John 13:2; I Corinthians 11:23-26; see John 6:31-58), and this begins to set it apart from a sin offering, which was not generally available for eating.
There is a conspicuous absence of any mention of forgiveness or atonement within the context of any Old Testament Passover. Instead, the Scriptures speak frequently of the Exodus Passover in terms of purchase or redemption. Israel was not redeemed from sin through the Passover, but only purchased from Pharaoh (Exodus 6:6; 15:13, 16; Deuteronomy 7:7-8; 9:26-29; 13:5; 15:15; 21:8; 24:18; II Samuel 7:23-24; Psalm 74:2; 77:15; 78:42-43; Isaiah 43:3; 51:10; Micah 6:4).
God, through Moses, warned Israel that all the firstborn in the land of Egypt shall die (Exodus 11:5), and that would have included Israelite firstborn, too. The threat against the Israelites was real, and they had to prove to God, through the sign of the blood on the doorposts, that they wanted to be separate from the Egyptians. Without the blood, the Israelite firstborn would have shared in the same judgment as the Egyptian firstborn.
The blood on the doorposts represents the life of the lamb given to redeem those within each participating house (see Exodus 13:13-16; 34:19-20), not to symbolize forgiveness. God does not draw attention to the Israelites' sins in His Passover instructions, even though the Israelites were sinning - grievously, in fact. Through Ezekiel, God says that the Israelites as a whole were unabashed idolaters at this time, and God nearly destroyed them, then and there:
The Israelites not only had idols in Egypt, as this says, but other passages show that they were still carrying them in the wilderness. This means that some Israelites, maybe many of them, had idols in their homes even as they kept the Passover. That may be shocking, but what it shows is, first, God's incredible mercy, and second, that the Passover was not about cleansing Israel from sin, which requires repentance. The Passover had another purpose.
Now, why would God destroy one nation of idolaters (that is, Egypt) and yet deliver another nation of idolaters (that is, Israel)? God's displeasure in Ezekiel is obvious, and He gives no hint that the blood of the Passover lamb was for atonement. Israel's sins weren't being dealt with - God was overlooking them. This is why, according to Strong's, the Hebrew word for Passover (pesach) means, a pretermission; [that is, an] exemption. The word pretermission is hardly used today, but it basically means, an omission. To pretermit means to let pass without mention or notice. It is similar to mercy or grace (see Numbers 14:19; Romans 9:15-18). When Israel was in Egypt, God passed over them and their sins. Moses says this in Exodus 12:27:
This exemption - this sparing; this act of mercy rather than justice - is not the same as paying for or removing their sins. Instead, God overlooked their sins. Thus, the Passover is a demonstration of God's gracious acceptance rather than atonement.
Now, we will switch gears and consider the irreconcilable differences between the Passover instructions with the sin offering instructions. These differences are pretty … . . .