Q. When and why did Jewish rabbis start celebrating the Passover Seder after sundown on 15 Nisan, which is the Feast of Unleavened Bread?
A. The Passover meal consists only of lamb, unleavened bread, and bitter herbs (Exodus 12:8) and is to be eaten after the sundown that marks the beginning of the 14th of Nisan. It’s to be eaten in haste as if preparing to leave in a hurry (Exodus 12:11).
The word seder means order in Hebrew and is a more leisurely commemorative meal during which all the events of Passover are retold in a specific order. It typically lasts several hours and is eaten on the 15th of Nisan based on the Lord’s instructions in Exodus 12:14.
The Passover festival was not celebrated during the 40 years the Israelites spent in the wilderness. According to Joshua 5:10-12 Passover and the Feast of Unleavened bread were first commemorated when the Israelites were camped outside Jericho after entering the promised land. This was also as the Lord had instructed (Exodus 12:25). Passover is claimed to be the world’s oldest continually celebrated religious observance.