Exodus 12:21-22

Then Moses called for all the elders of Israel, and said unto them, Draw out and take you a lamb according to your families, and kill the passover. {lamb: or, kid} And ye shall take a bunch of hyssop, and dip {it} in the blood that {is} in the bason, and strike the lintel and the two side posts with the blood that {is} in the bason; and none of you shall go out at the door of his house until the morning.