A number of Hebrew and Greek words describe that which is clean and pure as well as the act of purification, that is, restoring to a condition without blemish, spotless, free from anything that soils, adulterates, or corrupts. These words describe not only physical cleanliness but, more often, moral or spiritual cleanness. Often physical and ceremonial cleanness overlap. The Hebrew verb ta·herʹ (be clean; cleanse) usually refers to ceremonial or moral cleanness. A Hebrew synonym of ta·herʹ is ba·rarʹ, which, in its various forms, means “clean out; select; keep clean; show oneself clean; cleanse.” (Eze 20:38; Ec 3:18; Ps 18:26; Jer 4:11) The Greek word ka·tha·rosʹ, meaning “clean; pure,” is used in a physical, moral, and religious sense. (Mt 23:26; Mt 5:8; Tit 1:15) “Uncleanness” is derived from the Hebrew ta·meʼʹ and is a rendering of the Greek a·ka·thar·siʹa.—Le 5:3; Mt 23:27; Ga 5:19.
Physical Cleanness. Their personal habits made the nation of Israel a comparatively healthy people, notwithstanding their nomadic wanderings in the wilderness for 40 years. God’s laws governing their camp life, including the diagnosis and treatment of diseases, were unquestionably responsible for this. The importance of clean water was emphasized under this arrangement. Not all animals were classified as clean for food. (See ANIMALS.) Precautionary regulations governed the handling and disposal of dead bodies. Quarantines acted as barriers against the spread of contagious diseases. Sewage disposal by burying excreta was a sanitation requirement far in advance of the times. (De 23:12-14) The requirements of frequent bathing and the washing of clothes were also beneficial provisions in that nation’s code of laws.
The Scriptures often use physical cleanness as a symbol or representation of spiritual cleanness. For example, mention is made of “bright, clean, fine linen,” and it is said to represent “the righteous acts of the holy ones.” (Re 19:8) Jesus also drew upon a principle of physical cleanness when pointing out the spiritual uncleanness and hypocrisy of the Pharisees. Their deceitful conduct was likened to cleaning the outside of a cup or dish without doing the same thing to the inside. (Mt 23:25, 26) Jesus used a similar illustration during the last Passover meal when talking to his disciples with Judas Iscariot present. Even though they had bathed and had their feet washed by the Master, and were therefore “wholly clean” physically, yet spiritually speaking, “Not all of you are clean,” Jesus said.—Joh 13:1-11.
The Bible lists some 70 causes of physical uncleanness and ceremonial defilement. Among these are: contact with dead bodies (Le 11:32-40; Nu 19:11-19); contact with unclean persons or things (Le 15:4-12, 20-24; Nu 19:22); leprosy (Le 13:1-59); physical discharges of the sex organs, including emission of semen during sexual intercourse (Le 15:1-3, 16-19, 32, 33); childbirth (Le 12:1-5); eating the flesh of unclean birds, fish, or animals (Le 11:41-47). The priests were especially obligated to be physically as well as ceremonially clean when serving before Jehovah. (Ex 30:17-21; Le 21:1-7; 22:2-8) In a special sense the land could be polluted by acts of murder and idolatry.—Nu 35:33, 34; Eze 22:2-4; 36:25.
Ceremonial Cleanness. This was observed among the Israelites under the penalty of death. “You must keep the sons of Israel separate from their uncleanness, that they may not die in their uncleanness for their defiling of my tabernacle, which is in their midst.” (Le 15:31) Cleansing was usually performed by the use of water and ashes of a red cow, and the ceremony was administered in behalf of persons, places, and things. (Nu 19:2-9) Three of the most common causes of uncleanness involving persons are enumerated at Numbers 5:2: “ every leprous person and  everyone having a running discharge and  everyone unclean by a deceased soul.”
Leprosy. This was the most loathsome of all diseases and required severe measures of control, including prolonged isolation with careful and repeated examination to determine when a cure had been effected. (Le 13:1-46; De 24:8) It, therefore, required a great deal of faith for the unclean leper to say to Jesus: “Lord, if you just want to, you can make me clean.” Jesus not only wanted to but he also showed he had the ability to cure this loathsome disease by commanding: “Be made clean.” Jesus then told this restored man: “Go, show yourself to the priest, and offer the gift that Moses appointed.”—Mt 8:2-4; Mr 1:40-44; see LEPROSY.
Originally, under the prescribed regulations of the Law, before a cured victim of leprosy could return to normal living, an elaborate two-part ceremony was necessary, the first part involving the use of water, cedarwood, coccus scarlet material, hyssop, and two birds. These things were supplied by the recovered leper when he presented himself to the priest outside the camp of Israel. One of the birds was then killed over running water, and its blood was caught in an earthenware vessel. The cedar, scarlet material, hyssop, and the living bird were dipped in the blood; the cured leper was spattered seven times by the priest with the blood, and the live bird was turned loose. Upon being pronounced clean, the man shaved, bathed, washed his garments, and entered the camp, but he was required to dwell seven days outside his tent. On the seventh day he again shaved off all his hair, including his eyebrows. The next day he brought two rams and a female lamb, less than a year old, together with a little flour and oil, as a guilt offering, sin offering, burnt offering, and grain offering. The guilt offering consisting of one ram and the oil was first presented as a wave offering before Jehovah by the priest, who then killed the ram; he put some of its blood on the lobe of the right ear, the right thumb, and the right big toe of the one being cleansed. Similarly, some of the oil was then placed on top of the blood in the three above-mentioned places; some of the oil was also sprinkled seven times before Jehovah, and the balance of it was put on the head of the one being cleansed. The priest then offered up the sin, burnt, and grain sacrifices, making atonement and pronouncing the cured leper clean. If, because of circumstances, the candidate was very poor, he could substitute two turtledoves or two young pigeons for the lamb and one of the rams used as the sin and the burnt offerings.—Le 14:1-32.
Discharges. There were laws governing both the natural and diseased discharges from the bodies of both sexes, that is, discharges from the sex organs. If a man had an involuntary emission of semen during the night, he was to bathe and wash his garments and remain unclean until the following evening. A woman was to count seven days as the period of uncleanness for her regular menstruation.
However, if a woman had an irregular, abnormal, or prolonged flow, then she was to count also seven days after it stopped. So also the male was to count seven days after a running discharge had stopped. (Such diseased condition of his urinary system is not to be confused with his normal expulsion of semen.) Anything that the man or woman might touch or sit on (beds, chairs, saddles, garments, and so forth) during their state of uncleanness was itself made unclean, and in turn, anyone touching these articles or the unclean person himself was required to bathe, wash his garments, and remain unclean until evening time. In addition to bathing and washing their garments, both the male and female on the eighth day were to bring two turtledoves or two young pigeons to the tent of meeting, and the priest was to offer them, one as a sin offering and the other as a burnt sacrifice, to make atonement for the cleansed person.—Le 15:1-17, 19-33.
When a man and his wife had intercourse in which there was an emission of semen, they were required to bathe and were unclean until evening. (Le 15:16-18) If inadvertently a wife’s flow began during intercourse, then the husband was unclean seven days, the same as his wife. (Le 15:24) If they deliberately showed contempt for God’s law and had sexual relations while she was menstruating, the penalty of death was imposed on the male and the female. (Le 20:18) For the above reasons, when ceremonial cleanness was required, as, for example, when men were sanctified for a military expedition, they were obliged to refrain from having intercourse with their wives.—1Sa 21:4, 5; 2Sa 11:8-11.
Giving birth also meant a period of uncleanness for the mother. If the baby was a boy, she was unclean for seven days, the same as during her menstrual period. The eighth day the child was circumcised, but for another 33 days the mother was unclean with regard to touching anything holy or coming into the sanctuary, though she did not make unclean everything she touched. If the baby was a girl, this 40-day period was doubled: 14 days plus 66 days. Thus, from birth, the Law distinguished between male and female, assigning to the latter a subordinate position. In either case, at the end of the period of purification she was to bring a ram less than a year old for a burnt offering and a young pigeon or a turtledove for a sin offering. If the parents were too poor to afford a ram, as was the case with Mary and Joseph, then two doves or two pigeons served for the cleansing sacrifices.—Le 12:1-8; Lu 2:22-24.
Why did the Mosaic Law say that sexual intercourse and childbirth made a person “unclean”?
The question arises: Why were such normal, proper things as menstruation, sexual intercourse between married persons, and childbirth viewed in the Law as making one “unclean”? For one thing, it raised the most intimate relations of marriage to the level of sanctity, teaching both mates self-control, a high regard for the reproductive organs, and respect for the sacredness of life and blood. The hygienic benefits that accrued from scrupulous observance of these regulations have also been commented on. But there is yet another aspect of the matter.
In the beginning God created the sex impulses and generative powers in the first man and woman and commanded them to cohabit and bring forth children. It was therefore no sin for the perfect pair to have sexual intercourse. However, when Adam and Eve disobeyed God, not in the matter of sex relations, but in eating the forbidden fruit, drastic changes took place. Suddenly their guilty sin-stricken consciences made them aware of their nakedness, and they immediately covered their genital organs from God’s sight. (Ge 3:7, 10, 11) From then on, men could not carry out the procreative mandate in perfection, but, instead, the hereditary blemish of sin and the penalty of death would be transmitted from the parents to children. Even the most upright and God-fearing parents produce sin-infected children.—Ps 51:5.
The Law’s requirements pertaining to the functions of the reproductive organs taught men and women self-discipline, restraint of passions, and respect for God’s means of propagation. The Law’s regulations forcefully reminded creatures of their sinful state; these were not merely health measures to ensure cleanliness or prophylactic safeguards against the spread of diseases. As a reminder of man’s inherited sinfulness, it was fitting that both the male and the female with genital discharges due to normal functions of their bodies observe a period of uncleanness. If suffering abnormal prolonged discharges because of defective conditions, a more extensive period of uncleanness was demanded; and in the end, as also when a mother gave birth, in addition to bathing, a sin offering was necessary, so that God’s priest might make atonement in behalf of the person. Jesus’ mother Mary thus confessed to her hereditary sinfulness, acknowledging that she was not sinless, immaculate, by offering a sin-atoning sacrifice after giving birth to her firstborn.—Lu 2:22-24.
Dead bodies. Under the Mosaic Law governing dead bodies, there were different degrees of uncleanness: Touching a dead beast made one unclean for only the day; touching a dead man resulted in uncleanness for a week. In the first instance a person was required only to wash his garments, or in case he inadvertently ate an animal that had died of itself or had been torn by a wild beast, then he had to bathe in addition to washing his garments. (Le 5:2; 11:8, 24, 27, 31, 39, 40; 17:15) The same injunction was imposed upon the priests, with the further command that if while in an unclean state they ate anything holy, they were to be put to death.—Le 22:3-8.
For persons who touched a human corpse a more involved purification ceremony was necessary. For this purpose ashes were prepared by slaughtering a red cow outside the camp. The priest spattered some of its blood seven times toward the tent of meeting. The whole cow (skin, flesh, blood, dung) was then burned, and the cedarwood, hyssop, and coccus scarlet material were cast into the blaze. The ashes were kept and used “for the water for cleansing,” which on the third and seventh days was sprinkled for purification on the one touching the human corpse. At the end of the seven days he was to wash his garments and bathe, and he was then pronounced clean.—Nu 19:1-13.
Under this statute all persons who were in the house or tent when death occurred, as well as the dwelling itself and all open vessels, were made unclean. Touching even a bone of a dead man on the battlefield or touching any burial place, or sepulcher, likewise made one unclean. This is why in Jesus’ day it was customary to whitewash the graves a month before Passover in order to safeguard people against inadvertently stumbling upon a grave and thus becoming disqualified to partake of the feast. (Nu 19:14-19; Mt 23:27; Lu 11:44) The occurrence of human death in the presence or alongside of one under a Nazirite vow canceled out the time he had already spent under the vow, and it necessitated the offering of a sacrifice.—Nu 6:8-12; see NAZIRITE; SAMSON.
Under the Law covenant, places and things that were contaminated had to be cleansed. If a murder was committed by an unknown assailant, it was first determined by measurement which was the city nearest to the crime. The elders of that city then had to take a young unworked cow (as a substitute for the murderer) and break its neck in a torrent valley running with water, and over the animal they had to cleanse themselves symbolically of any responsibility by washing their hands in innocence, pleading that the charge of guilt be not laid to their account.—De 21:1-9.
Garments and vessels that came in contact with dead bodies or that were polluted in other ways had to be cleansed according to prescribed formulas. (Le 11:32-35; 15:11, 12) The development of leprosy in a garment or in the walls of a house was a much more serious matter, for if it could not be contained and seemed to spread, it was necessary to destroy the garment or tear down the house completely.—Le 13:47-59; 14:33-53.
Spoils of war had to be cleansed before they could be brought in. Combustible articles were washed with water, but metal objects had to pass through the fire.—Nu 31:21-24.
Christian Cleanness. Christians are not under the Law and its cleansing requirements, even though such Law and its customs were still in force in the days when Jesus was on earth. (Joh 11:55) The Law had “a shadow of the good things to come”; ‘the reality belongs to Christ.’ (Heb 10:1; Col 2:17) Hence, Paul wrote concerning these purification matters: “Yes, nearly all things are cleansed with blood according to the Law [Moses sprinkled the book, the people, the tent, and the vessels with blood], and unless blood is poured out no forgiveness takes place. Therefore it was necessary that the typical representations of the things in the heavens should be cleansed by these means.” “For if the blood of goats and of bulls and the ashes of a heifer sprinkled on those who have been defiled sanctifies to the extent of cleanness of the flesh, how much more will the blood of the Christ, who through an everlasting spirit offered himself without blemish to God, cleanse our consciences from dead works that we may render sacred service to the living God?”—Heb 9:19-23, 13, 14.
So it is the blood of the Lord Jesus Christ that cleanses Christians from all sin and unrighteousness. (1Jo 1:7, 9) Christ “loved the congregation and delivered up himself for it, that he might sanctify it, cleansing it with the bath of water by means of the word” in order for it to be spotless, holy, and without blemish, “a people peculiarly his own, zealous for fine works.” (Eph 5:25-27; Tit 2:14) Every member of this Christian congregation, therefore, should not “become forgetful of his cleansing from his sins of long ago” but should continue to manifest the fruitage of God’s spirit (2Pe 1:5-9), remembering that “every one bearing fruit he [God] cleans, that it may bear more fruit.”—Joh 15:2, 3.
Christians must, therefore, maintain a high standard of physical, moral, and spiritual cleanness, guarding against “every defilement of flesh and spirit.” (2Co 7:1) In view of what Jesus said, that it is ‘not what enters a man but what comes forth from him that defiles,’ these beneficiaries of the cleansing blood of Christ place the greater emphasis on spiritual cleanliness. They maintain “a clean heart” and “a clean conscience” before God. (Mr 7:15; 1Ti 1:5; 3:9; 2Ti 1:3) To such ones with a clean conscience “all things are clean,” in contrast with faithless persons who are defiled in conscience, to whom “nothing is clean.” (Tit 1:15) Those who want to remain clean and pure in heart heed the counsel of Isaiah 52:11, which says: “Touch nothing unclean; . . . keep yourselves clean, you who are carrying the utensils of Jehovah.” (Ps 24:4; Mt 5:8) Doing this, their “hands” in a figurative sense are cleansed (Jas 4:8), and God deals with them as clean persons.—2Sa 22:27; Ps 18:26; see also Da 11:35; 12:10.
On one occasion the apostle Paul, though no longer under the Law, observed the Law’s requirements by ceremonially cleansing himself at the temple. Was this inconsistent on his part? Paul did not fight against the Law or its procedures; he merely showed that obedience to it was not divinely required for Christians. Where its procedures did not violate new Christian truths, there was no real objection to doing what God had prescribed under the Law. Paul took the action he did so that he might not needlessly hinder the Jews from listening to the good news about Jesus Christ. (Ac 21:24, 26; 1Co 9:20) In a similar vein the apostle also argued that food in itself may be clean, but if his eating of it stumbled his brother, then he would refrain from eating. (Ro 14:14, 15, 20, 21; 1Co 8:13) In all of this, Paul showed a great concern for the salvation of others and did everything in his power to bring this about. He therefore could say: “I am clean from the blood of all men.”—Ac 20:26; 18:6.