Exodus 12:7, 22-23

Moreover, they shall take some of the blood and put it on the two doorposts and on the lintel [above the door] of the houses in which they eat it. [Matt 26:28; John 1:29; Heb 9:14]

You shall take a bunch of hyssop, dip it in the blood which is in the basin, and touch some of the blood to the lintel [above the doorway] and to the two doorposts; and none of you shall go outside the door of his house until morning. For the LORD will pass through to strike the Egyptians; and when He sees the blood on the lintel [above the entry way] and on the two doorposts, the LORD will pass over the door and will not allow the destroyer to come into your houses to slay you.