The ritual of the red heifer (Numbers 19:1-21) prescribes the process for cleansing someone who has become unclean from touching a corpse (19:11-12). It is quite detailed. It required a red heifer without fault or blemish that had never borne a yoke (19:2). Unlike all the sacrifices that took place in or near the sanctuary, the heifer had to be slaughtered outside the camp; its blood would be sprinkled in the direction of the Tent of Meeting; and then the heifer was burnt whole, along with cedar wood, hyssop, and crimson material (19:3-6).

It is not certain what plant is in mind when the Bible mentions hyssop (Hebrew אזוב ezov; Greek ὕσσωπος hyssopos); it appears to be different from the plant we call hyssop today. One candidate proposed by scholars is the caper plant, from the similarity of the Hebrew ezov to the Arabic name of the caper, azaf. The caper plant has a pinkish-red flower. If that identification is correct, then we have a ceremony where a red cow is completely burned up, along with red wood, red flowers, and red cloth.

The ashes from this fire would then be preserved, and used in making the “water of cleansing” (19:9). The text in Numbers simply suggests that a certain amount of this ash would be added to water. In the Mishnah, Jewish tradition adds the requirement that this be spring water, and it specifies extraordinary efforts to ensure that no contact with anything dead takes place in the gathering of the water (Parah 3).

This text is commonly cited by rabbis as an example of a חק (ḥok): a commandment where we really don’t know how the thing is supposed to work. This contrasts with the laws regarding leprosy, in that we can see how those laws are designed to prevent the spread of disease; but how are all these details about the sacrifice of a heifer supposed to make a difference in creating this water of purification? We could guess about the symbolism: the red things are burned up to form white ash, an idea which possibly is echoed in Isaiah’s prophecy some six centuries later: “though your sins are like scarlet, they shall be like snow” (Isaiah 1:18). But all of this detail given in today’s reading is for the apparently-minor task of cleansing someone who has become unclean just from touching a dead body. In the end, all we know about a ḥok is that we can’t explain why it is there, but it is still a command that comes from God.

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We are not good at obedience, Lord, even when we do understand the reason behind your instructions; yet we seem especially resistant when we can’t see the purpose of your command. Grant us the courage and diligence to follow you, we pray, even when we have not yet understood where you are leading us.