If you're following the comments on this post, you will note that one of the readers (Chris) has argued that the rules for the Passover in the book of Exodus weren't really rules - Exodus only described a memorial. Therefore, the rules in Deuteronomy were the "real"...
Exodus 12
Example #2 – Changes in Passover Laws
This is long, but bear with me. There’s a discussion payoff at the end. The Three Annual (Required) Festivals for Israelites in the Book of Exodus are: Passover / Unleavened Bread (the month of Abib was renamed to Nisan during exilic times) Harvest (qatsir)...