Exodus 12:12-14

Amplified Bible

¹² For I [the Lord] will pass through the land of Egypt on this night, and will strike down all the firstborn in the land of Egypt, both man and animal; against all the gods of Egypt I will execute judgments [exhibiting their worthlessness]. I am the Lord. ¹³ The blood shall be a sign for you on [the doorposts of] the houses where you live; when I see the blood I shall pass over you, and no affliction shall happen to you to destroy you when I strike the land of Egypt.^(A)

Feast of Unleavened Bread

¹⁴ ‘Now this day will be a memorial to you, and you shall keep it as a feast to the Lord; throughout your generations you are to celebrate it as an ordinance forever.