Exodus 12:22-24

Complete Jewish Bible

²² Take a bunch of hyssop leaves and dip it in the blood which is in the basin, and smear it on the two sides and top of the door-frame. Then, none of you is to go out the door of his house until morning. ²³ For Adonai will pass through to kill the Egyptians; but when he sees the blood on the top and on the two sides, Adonai will pass over the door and will not allow the Slaughterer to enter your houses and kill you. ²⁴ You are to observe this as a law, you and your descendants forever.