Exodus 12:21-23 NIV

21 Then Moses summoned all the elders of Israel and said to them, "Go at once and select the animals for your families and slaughter the Passover1 lamb.

References for Exodus 12:21

22 Take a bunch of hyssop,2 dip it into the blood in the basin and put some of the blood3 on the top and on both sides of the doorframe. Not one of you shall go out the door of his house until morning.

References for Exodus 12:22

23 When the LORD goes through the land to strike4 down the Egyptians, he will see the blood5 on the top and sides of the doorframe and will pass over6 that doorway, and he will not permit the destroyer7 to enter your houses and strike you down.

References for Exodus 12:23