Moses called for all the elders of Israel
and said to them,

    "Pick out lambs for yourselves
    according to your families,

    and kill the Passover lamb. 
You shall take a bunch of hyssop,

    dip it in the blood in the basin,
    and strike the lintel and the two
 doorposts.  
None of you shall go out of 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 
and on the two doorposts,
the Lord will pass over the door
    and 
not allow the destroyer
    to come into your houses to strike you.
 
                                            --- Exodus 12:21-23