A ceremonially unclean person was barred from the sanctuary or Temple (cf. Lev 12:4; Num 19:13, 20), and might not touch any sacred object for the duration of his uncleanness (cf. Num 19:22). Anyone who touched an unclean person during this time also became unclean and must bathe himself, wash his clothes, and be unclean for the remainder of that day. Then he was clean again "at even" (ch 19:19), that is, "when the sun is down" (Lev 22:6, 7).
Whatever the unclean person might touch similarly became unclean. And anyone who touched what an unclean person had touched was also considered ceremonially unclean for the remainder of that day. For each category of uncleanness a ritual procedure of purification was specified.
1. Purification from uncleanness incurred by contact with a corpse (Num 19). Procedure for the removal of ceremonial defilement incurred from touching a dead body, a bone, or a grave, was as follows: In preparation for the ceremony proper, an unblemished red heifer which had never worn a yoke was taken to the priest, who accompanied the heifer and its master to an appropriate spot outside the camp. The heifer was then slaughtered in the presence of the priest, who dipped his finger into the blood that had been preserved and sprinkled the blood toward the sanctuary 7 times. The whole animal was then burned with fire, into which the priest cast cedarwood, scarlet material, and hyssop. A ceremonially clean person then gathered up the ashes of the heifer and stored them in a ceremonially clean place outside the camp. The man who slew the heifer and the priest who participated in this ritual thereby became ceremonially unclean, and accordingly were to wash their clothing, bathe, return to camp, and regain ceremonial cleanness at the close of the day. A person ceremonially defiled by contact with a dead body, bone, or grave, remained ceremonially unclean for 7 days. On the 3rd and 7th days he was to be sprinkled with water mixed with ashes of the red heifer, by any ceremonially clean person. A bunch of hyssop was used for sprinkling the water. On the 7th day the person defiled by contact with the dead was to bathe, wash his clothes, and regain ceremonial cleanness at the close of the day. The clean person officiating in this rite was to wash his clothes, but continued to be ceremonially unclean for the remainder of the day. The tent and furnishings of the unclean person were likewise to be sprinkled with water containing the ashes of the red heifer, and after 7 days were again considered ceremonially clean. This water is called "water of separation" (KJV) and "water for impurity" (RSV).
A Nazirite defiled by contact with a corpse was likewise to remain unclean for 7 days. But on the 7th day he was to shave his hair, the sign of the vow he had taken, and on the 8th day to present 2 young turtledoves or pigeons, one for a sin offering and the other for a burnt offering, and a lamb for a trespass offering. He forfeited credit for the days of his vow prior to the defilement, and was required to begin the entire period over again (Num 6:9-12).
2. Purification from contact with the carcass of an unclean animal (see Lev 11:29-31, 39). No ritual was specified for the person thus defiled, but he was to be ceremonially unclean until the close of the day (cf. v 40).
3. Uncleanness incurred by issues from the generative organs (Lev 15). These issues might be either normal or abnormal. A person thus defiled was considered unclean for 7 days from the time that the issue stopped. On the 7th day he was to bathe in running water and wash his clothes. At the close of the day he again became ceremonially clean. On the 8th day he was to present himself at the sanctuary, later the Temple, with two turtledoves or pigeons, one for a sin offering and the other for a burnt offering. Physical contact with someone thus in a state of ceremonial uncleanness, or contact with anything he had touched, rendered another person unclean. The latter, however, was to bathe himself, and he regained ceremonial cleanness at the end of that day.
4. Purification of a mother at childbirth (Lev 12). The mother was to remain ceremonially unclean for 7 days in the case of a male child, and 14 days in the case of a female child, plus 33 additional days for a male child and 66 additional days for a female child. At the close of the specified period of time the mother was to present a lamb for a burnt offering and a turtledove or a pigeon for a sin offering. If she was poor, only young birds were required, one for a burnt offering and the other for a sin offering (see Lk 2:21-24).
5. Purification from defilement by leprosy (Lev 14). When cure from leprosy had been certified, "two birds alive and clean," together with cedarwood, scarlet material, and hyssop, were presented. One bird was killed over an earthen vessel filled with running water and its blood was permitted to drain into the water. The priest then dipped the living bird, the cedarwood, the scarlet material, and the hyssop into the water containing the blood of the bird that had been killed. This water was then sprinkled upon the leprous person 7 times, and following that the living bird was set free. The healed leper was then to wash his clothes, shave off all his hair, bathe, and return to camp, but was forbidden to enter his tent or house for 7 days. On the 8th day he was to present himself at the sanctuary with 2 male lambs, one for a trespass offering and the other for a burnt offering, together with a ewe lamb for a sin offering. He was also to bring a portion of flour mingled with oil for a meal offering, together with an extra container of oil. The trespass offering was slain and waved before the Lord, together with the pot of oil. The priest next touched some of the blood of the trespass offering to the right ear, right thumb, and right great toe of the offerer. He then sprinkled the oil 7 times before the Lord, and touched it also to the healed leper's right ear, thumb, and toe. The remainder of the oil he poured upon the head of the offerer. Finally, he offered the sin offering, and the burnt offering and its accompanying meal offering. In case of poverty, 1 lamb with the oil and flour, would suffice for a trespass offering, and 2 turtledoves or pigeons, one for a sin offering and the other for a burnt offering -- Seventh-day Adventist Dictionary.