Deuteronomy 16:1

1 “Observe the month of Abib
March-April; called Nisan in the post-exilic period; Neh 2:1; Est 3:7
,
b and celebrate the
Passover: The Israelite festival celebrated on the fourteenth day of the first month in the early spring. It was a celebration of the deliverance of the Israelites from Egypt, commemorating the final plague on Egypt when the firstborn were killed.
Passover to the Lord your God, because the Lord your God brought you out of Egypt by night in the month of Abib.
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