God commands the Israelites to slaughter and eat a lamb, using it's blood to mark their doors so he will know to "pass over" their homes.
Question, God has spared the Israelites from the rest of the plagues without special preparation. Why do it now?
To me this seems like an insertion into the story to explain dogma.
I believe it is also the first of God's VERY specific instructions to his people (not counting Noah, an individual).
"for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel." Again God's rules seem AWFULLY harsh.
We also see a repeating of the same rule. Exodus 12:15 and 12:19. And Exodus 13 REALLY drives it home. OK, we get it! ;-)
Mosses finally looks like a worthy prophet as he commands the Israelites out of Egypt and across the Red Sea. And Moses and the Israelites lived happily ever after. Right?