Exodus 12:24

20 You are not to eat anything leavened; eat unleavened bread in all your homes.”

21 Then Moses summoned all the elders of Israel and told them, “Go at once and select for yourselves a lamb for each family, and slaughter the Passover lamb.

22 Take a cluster of hyssop, dip it into the blood in the basin, and brush the blood on the top and sides of the doorframe. None of you shall go out the door of his house until morning.

23 When the LORD passes through to strike down the Egyptians, He will see the blood on the top and sides of the doorframe and will pass over that doorway; so He will not allow the destroyer to enter your houses and strike you down.

24 And you are to keep this command as a permanent statute for you and your descendants.

25 When you enter the land that the LORD will give you as He promised, you are to keep this service.

26 When your children ask you, ‘What does this service mean to you?’

27 you are to reply, ‘It is the Passover sacrifice to the LORD, who passed over the houses of the Israelites in Egypt when He struck down the Egyptians and spared our homes.’” Then the people bowed down and worshiped.

28 And the Israelites went and did just what the LORD had commanded Moses and Aaron.

Read all of Exodus 12