In reply to Eric Meyer’s recent post:
Most of the modern seder is based upon God’s explicit instructions as recorded in Exodus. Below are some comments I wrote on the subject: Seder and the Night of Deliverance
Now, I must admit that Exodus 12:23-27 basically says to observe the ceremony of spreading lamb’s blood on the door frames as a “lasting ordinance”. However, most Jews today also do not observe the Sin Offerings, Guilt Offerings, and Burnt Offerings as depicted in Leviticus 5 and elsewhere, probably more out of practicality than out of indifference.
Of course, Christians today do not observe these instructions because Christ fulfilled the laws of Moses and became the last sacrifice.