Parah 11:7-8

Parah 11:7

Any species of hyssop that is called by a descriptive name is invalid, while plain hyssop is valid. Medicinal hyssop, blue hyssop, Roman hyssop and desert hyssop are invalid. Hyssop that is ritually-unclean trumah is invalid; hyssop that is ritually-clean trumah may not be used to sprinkle the sanctification water but if one did so, it is valid. The sprinkling may not be performed with young shoots or berries, though one is not liable for entering the Temple after being sprinkled with young shoots. Rabbi Eliezer says that one is also not liable if he was sprinkled with the berries. “Young shoots” means stalks that have not yet ripened.

Parah 11:8

Hyssop with which one sprinkled the sanctification water may be used to purify a metzora (colloquially a “leper,” but not really). If the hyssop was gathered for firewood and liquid fell on it, it may be dried and it’s valid. If it was gathered for food and liquid fell on it, then even if one dries it, it’s invalid. Rabbi Meir says that if it was gathered for sprinkling the sanctification water, the rules are the same as if one gathered it for food. Rabbi Yehuda, Rabbi Yosi and Rabbi Shimon all agree that the rules are the same as if one gathered it for firewood.