hyssop is a sacred plant used in judaism. it appears a lot in the hebrew bible as ezov. in exodus 12:22 the jews in egypt are instructed to "take a bunch of hyssop, dip it into the blood in the basin and put some of the blood on the top and on both sides of the doorframe. not one of you shall go out the door of his house until morning." it is used by the priests in the temple of solomon for purification rites of various kinds in leviticus 14:4-7, 14:49-52, 19:6, 18. hyssop is also often used to fill the catholic ceremonial aspergillum, which the priest dips into a bowl of holy water, and sprinkles onto the congregation to bless them. however, researchers say that the biblical accounts refer not to the plant currently known as hyssop. it might actually be one of a number of different herbs.