Exodus 12:42
It is a night to be much observed to the LORD for bringing them out from the land of Egypt. This is that night of the LORD, to be much observed of all the children of Israel throughout their generations.
Deuteronomy 16:1-6
Observe the month of Abib, and keep the Passover to the LORD your God; for in the month of Abib the LORD your God brought you forth out of Egypt by night.
Exodus 12:14
This day shall be to you for a memorial, and you shall keep it a feast to the LORD: throughout your generations you shall keep it a feast by an ordinance forever.
Exodus 13:10
You shall therefore keep this ordinance in its season from year to year.