While Leviticus focuses specifically on the Law itself, and was almost certainly written by Moses himself, Numbers focuses on the day to day life of Israel during this period and may have been recorded by others, based on what they experienced and observed. Since death was a common occurrence, some as a result of plagues, guidelines for preventing the spread of disease would become generally known. The preparation and use of the water of separation was an important element of these guidelines.
“And the LORD spake unto Moses and unto Aaron, saying, This is the ordinance of the law which the LORD hath commanded, saying, Speak unto the children of Israel, that they bring thee a red heifer without spot, wherein is no blemish, and upon which never came yoke: And ye shall give her unto Eleazar the priest, that he may bring her forth without the camp, and one shall slay her before his face: And Eleazar the priest shall take of her blood with his finger, and sprinkle of her blood directly before the tabernacle of the congregation seven times: And one shall burn the heifer in his sight; her skin, and her flesh, and her blood, with her dung, shall he burn: And the priest shall take cedar wood, and hyssop, and scarlet, and cast it into the midst of the burning of the heifer.
Then the priest shall wash his clothes, and he shall bathe his flesh in water, and afterward he shall come into the camp, and the priest shall be unclean until the even. And he that burneth her shall wash his clothes in water, and bathe his flesh in water, and shall be unclean until the even.” (Numbers 19:1-8)
A healthy young red colored cow was to be killed outside the camp. The priest was then to dip his finger in her blood and sprinkle it seven times in front of the Tabernacle. The entire body of the heifer was then to be burned outside the camp, saving the ashes. In the process, cedar wood, hyssop , and scarlet, the bodies of the insects from which the dye was obtained were to be burned as well. Both the priest, and the man who burned the body were to bathe and remain in quarantine for the remainder of the day.
“And a man that is clean shall gather up the ashes of the heifer, and lay them up without the camp in a clean place, and it shall be kept for the congregation of the children of Israel for a water of separation: it is a purification for sin. And he that gathereth the ashes of the heifer shall wash his clothes, and be unclean until the even: and it shall be unto the children of Israel, and unto the stranger that sojourneth among them, for a statute for ever.” (Numbers 19:9-10)
Another person, who had had no contact with death or other potential source of contamination was to then gather the ashes and store them so they would not be contaminated. When mixed with water, a mild lye solution would result, suitable for use as a disinfectant. The person responsible for gathering the ashes was to wash his clothing and remain in quarantine until evening as well. While les stringent, the process resembles modern procedures to prevent contamination in production of medical supplies, protecting both the product, and the workers who produce it. The standard was to be applied whether produced by an Israelite or one from another country.
“He that toucheth the dead body of any man shall be unclean seven days. He shall purify himself with it on the third day, and on the seventh day he shall be clean: but if he purify not himself the third day, then the seventh day he shall not be clean. Whosoever toucheth the dead body of any man that is dead, and purifieth not himself, defileth the tabernacle of the LORD; and that soul shall be cut off from Israel: because the water of separation was not sprinkled upon him, he shall be unclean; his uncleanness is yet upon him.” (Numbers 19:11-13)
Regardless of the cause of death, anyone who touched a dead person was to be considered unclean and avoid public contact for seven days. On the third day of isolation his clothing and skin were to be cleansed with the water of separation. Failure to apply the disinfectant meant that they could not be sure no pathogens were still carried, and the person was to be isolated for refusing to protect others.
“This is the law, when a man dieth in a tent: all that come into the tent, and all that is in the tent, shall be unclean seven days. And every open vessel, which hath no covering bound upon it, is unclean. And whosoever toucheth one that is slain with a sword in the open fields, or a dead body, or a bone of a man, or a grave, shall be unclean seven days.” (Numbers 19:14-16)
Since some diseases do not require actual contact, and some may be infectious without yet having caused symptoms in a person, provision was made to prevent the spread of such pathogens. Those who had possibly been exposed to such pathogens were also considered unclean, and open containers were to be considered contaminated.
“And for an unclean person they shall take of the ashes of the burnt heifer of purification for sin, and running water shall be put thereto in a vessel: And a clean person shall take hyssop, and dip it in the water, and sprinkle it upon the tent, and upon all the vessels, and upon the persons that were there, and upon him that touched a bone, or one slain, or one dead, or a grave: And the clean person shall sprinkle upon the unclean on the third day, and on the seventh day: and on the seventh day he shall purify himself, and wash his clothes, and bathe himself in water, and shall be clean at even.
But the man that shall be unclean, and shall not purify himself, that soul shall be cut off from among the congregation, because he hath defiled the sanctuary of the LORD: the water of separation hath not been sprinkled upon him; he is unclean.
And it shall be a perpetual statute unto them, that he that sprinkleth the water of separation shall wash his clothes; and he that toucheth the water of separation shall be unclean until even. And whatsoever the unclean person toucheth shall be unclean; and the soul that toucheth it shall be unclean until even.” (Numbers 19:17-22)
When disinfection was needed, the ashes were to be mixed with pure, not stagnant water, and sprinkled on everything which may have been contaminated including the skin of those who had come in contact with the dead person and allowed to remain for four days, after which everything was to be washed. If mixed in advance, the solution might well be contaminated, and since it was corrosive it could cause damage, so any one who came in contact with it was to be considered unclean and clean themselves. Refusal to apply the water of separation isolated one from the congregation of Israel.
Following these sanitary measures protected Jewish communities from most of the plagues of the Middle ages. As a result, many European leaders blamed the Jews for the severity of the plagues and the pogroms resulted. Some of the hatred remains today. Antiseptics and disinfectants were not widely used in European medicine until Joseph Lister began using them in the late 1800’s.
Just as the water of separation was required to be clean, cleansing by Christ is essential for Christian lives to be clean. Refusal to accept his cleansing makes us unfit to come into the presence of God and requires isolation from the church, as described in I Corinthians 5 and Matthew 18.