A holy God wants a holy people. He had described the nation of Israel as holy (cf. Exod. 19:5–6) but also wanted them to live holy lives and grow increasingly holy. Holiness came, in part, by keeping the law; an important part of the law was the concept of cleanness.

Old Testament

Since Israel could become holy only by being clean, it is no surprise that the law’s first mention of prohibited food is accompanied by a command to be God’s holy people (Exod. 22:31). Nor is it unexpected that when God explains the laws about clean and unclean food, he tells the Israelites twice to “be holy, because I am holy” (Lev. 11:44–47).

Cleanness (Heb. tahor) does not refer to good hygiene, nor is it synonymous with morality, since a person could be unclean and still righteous. Cleanness allowed the OT believer to live a holy life and enabled that person to be made increasingly holy by “Yahweh, your sanctifier” (NIV: “the Lord, who makes you holy,” Lev. 20:8; cf. 21:8, 15, 23; 22:9, 16, 32; 31:13). Before considering how ritual purity led to holiness, we should summarize the purity laws themselves.

Purity laws. Impurity traveled along four channels: sexuality (e.g., nocturnal emission, menstruation, childbirth), diet (e.g., eating certain types of animals), disease (e.g., skin diseases, mildew), and death (i.e., contact with animal or human corpses). Impurities occurring naturally and unavoidably in the course of life (e.g., menstruation) were tolerated, representing no danger to the person or community as long as they were promptly addressed. Other impurities had to be avoided at all costs or else grave consequences would result to the person and community.

Tolerated impurities. We can further divide tolerated impurities into minor and major. Minor impurities resulted from touching an animal carcass or touching someone with a major impurity. Minor impurities did not make one contagious and could be addressed simply. Major impurities resulted from touching a human corpse, having a skin disease, or experiencing a nocturnal emission or menstruation. With these, one became “contagious,” purification took longer, and a sacrifice was required.

In order to become clean, the contaminant must be removed, with removal occurring in different ways. Tolerated impurities were removed by washing (bathing, laundering clothes, and sprinkling with water). What could not be washed away must be physically taken away, whether through burial, burning, or removal from the camp (e.g., scapegoat; Lev. 16:20–22).

Cleansing took time; generally the more serious the impurity, the longer the time, from one day for those who touch a dead animal, up to eighty days following the birth of a female child. Some tolerated impurities required sacrifices, with the animal’s blood being sprinkled against the side of the altar and poured out at its base (Lev. 5).

Ritual actions might accompany the sacrifices. For example, a person who had been healed of a contagious skin disease was to bring two live, clean birds to the priest. One bird was to be killed and its blood mixed with water, which was then sprinkled on the person. The other bird was dipped into the blood/water mixture and released, symbolizing the removal of the uncleanness. In the ritual of the red heifer (Num. 19), a combination of water and ashes was used to purify those who had touched a corpse.

Impurities to be avoided. Unlike the tolerated impurities that could not be avoided, certain objects and actions were completely off-limits to the holy people of God. Intentional violation brought more serious consequences, even being “cut off” from the community. Although it is unclear exactly what it meant to be cut off—perhaps excommunication, capital punishment, vulnerability to an untimely death, loss of progeny, or separation from one’s ancestors after death—the threat was ominous.

One prohibited impurity arose from eating food declared off-limits by God. All meat had to be thoroughly bled before being eaten (Gen. 9:3–4; Lev. 17:10–14; Deut. 12:16, 23). Edible land animals must both have a completely divided hoof and chew the cud (Lev. 11:3; Deut. 14:6), while water creatures had to have both fins and scales (Lev. 11:9; Deut. 14:9). Most birds were acceptable for food (exceptions are given in Lev. 11:13–19; Deut. 14:11–18), as were most insects (Lev. 11:20–23; Deut. 14:19–20) and some crawling animals (Lev. 11:29–31, 41–42).

Other prohibited impurities included what might be more readily identified as sinful acts. Sexual immorality (Lev. 18:6–25), idolatry (20:2–5), consulting mediums (20:6), and murder (Num. 35:33–34) defiled people and land. If such offenses were not “cleansed,” God would judge, whether by natural disaster (Isa. 24:1–13) or exile (Isa. 64:6–7; Mic. 2:10).

Reasons for the laws. Why did God declare certain things clean and others unclean? Some suggest that the distinction is arbitrary; the rules are given as a test of obedience. Others argue that the original audience knew of reasons now lost to us. Still others believe that God was protecting his people from disease. It is true that certain kinds of meat improperly prepared can transmit disease, but not all laws can be explained this way. Some believe that God identified things as clean because they represented a state of normalcy (e.g., fish normally propel themselves with fins, so those lacking fins are abnormal and thus unclean). A related view considers things as clean or unclean based on what they symbolized. So, for example, God identified objects as unclean if they were associated with death (e.g., vultures, corpses) because he is for life. Here again, it is difficult to explain all the laws by appeal to normalcy or symbolism.

Cleanness and holiness. While we may not know for certain why God chose these particular laws, we can see how they helped his people become holy.

First, these laws made possible access to the sanctuary, where holiness could be expressed and developed. The law of Moses contains repeated and stern reminders that those who are unclean may not “go to the sanctuary” (Lev. 10:10; 12:4; 15:31; Num. 19:13, 20). Only the clean could approach a holy God and participate in the rituals that demonstrated and developed their holiness.

Second, these rituals also fostered holiness by teaching the Israelites about impurity. Israel’s neighbors associated impurity with demons, but God indicated that it would be an Israelite’s uncleanness, not demonic activity, that kept that person from living a holy life.

Third, these purity laws taught the Israelites about the holy God, whom they were to imitate. If even innocent and otherwise good experiences prevented their association with him, God must be very holy indeed. These laws also reinforced God’s authority over every aspect of their lives. He determined when they could come to the sanctuary, but also what they could eat and when they could have sexual intercourse. These laws also reminded Israel that it was this same God who had provided a way to be clean and thereby holy. Cleansing was costly and humbling, but it was possible, coming as a gracious gift from God.

Fourth, a very practical consequence of these laws was to keep the Israelites separate from their neighbors. Not only were the Israelites to avoid pagan practices (e.g., rituals associated with mourning the dead; Lev. 19:27), but also they were to limit social contact with their pagan neighbors. Laws governing what could be eaten and how those animals must be slaughtered would help see to that. God was concerned that his people not be corrupted by their neighbors (cf. Deut. 7:1–6; 14:1–3).

New Testament

Ceremonial cleansing appears in the opening chapters of the Gospels. Mary underwent the required purification rituals after Jesus’ birth (Luke 2:22–24), and Jesus “cleansed” people from leprosy, instructing them to carry out the Mosaic purification rituals (Matt. 8:2–4; Mark 1:40–42; Luke 5:12–14; 17:11–19; cf. Matt. 10:8; 11:5; Luke 4:27; 7:22).

In one of his confrontations with the Pharisees, Jesus signaled a departure from how these laws had been practiced. He announced, “Nothing outside a person can defile them by going into them. Rather, it is what comes out of a person that defiles them” (Mark 7:15), to which Mark adds an explanation: “In saying this, Jesus declared all foods ‘clean’ ” (7:19). Peter’s rooftop vision in Acts 10 reflects this same perspective, as do the church’s decision regarding Gentile conversion (Acts 15) and Paul’s comments to the church at Rome (Rom. 14:14, 20–21).

The NT identifies the church as God’s holy people, called to be holy as he is holy (1 Pet. 1:16). Holiness still required purity, now manifested more ethically than physically. That is, one became unclean through sinful actions such as lying (1 Thess. 2:3) and licentiousness (Eph. 4:19) rather than by, for example, contact with a corpse. In the OT, all Israel was declared holy but was to live out that holiness in daily life. Purity came through ritual actions such as sacrifice and washing, with the assistance of a priest. So it is in the NT, though the sacrifice is now the once-for-all offering of Christ on the cross (Heb. 9:13–14; 1 John 1:7) as applied in the waters of baptism (Eph. 5:26; 1 Pet. 3:21) and assisted by Jesus the great high priest and by the priesthood of believers (2 Cor. 7:1; Heb. 4:14; James 4:8; 1 Pet. 1:22). Thus purified, believers can go on to live holy lives and become increasingly holy. Although the Testaments differ on the causes and solutions for uncleanness, they agree that a holy people has always been God’s goal, and that cleanness is a means to that end.