Impurity is the condition of being defiled in some sense. The word impurity can also refer to the contaminant itself: an unwanted substance that makes something unclean. The concepts of purity and impurity are important in the Bible’s presentation of holiness.
Under the rituals of the Old Testament Law, the Israelites were often confronted with the ideas of ritual or ceremonial purity and impurity. Many things could make an Israelite ritually unclean or impure: e.g., menstruation, childbirth, nocturnal emissions, touching a corpse, and certain types of skin diseases. Eating an unclean food would make one impure (see Acts 10:14). Impurity could be ceremonially passed to others: any personal contact with someone unclean would make a person unclean himself. There were so many ways one could become unclean that every Israelite, male and female alike, was sure to spend at least some time in a state of ceremonial impurity.
When someone had a ceremonial impurity and was declared unclean, he or she was separated from the community and not allowed to worship at the temple during the period of the impurity or uncleanness (Numbers 5:1–4). God’s Law provided a path to restore purity, however. The process of purification depended on the degree of impurity and ranged from physical washing to offering an animal sacrifice to atone for the uncleanness. The Law’s insistence on purity and its quarantine of impurity laid stress on the fact that God expected holiness in His people. He had chosen Israel to be in special relationship with Him. God is holy, and He demands holiness of the people who follow Him. “A little leaven leavens the whole lump” (Galatians 5:9, ESV); a little impurity negates integrity; a little sin destroys holiness.
In the Bible, ceremonial impurity can illustrate moral impurity. One vivid example of this is leprosy—one of the skin diseases that rendered a person ceremonially impure or unclean. Because there was no cure for leprosy, a person who contracted leprosy was often permanently unclean. Lepers were outcasts for life. They were not permitted to associate with others due to the contagiousness of their disease; they could not live with their families or worship at the temple or work at jobs. Their impurity was so severe that, if they were in a public area, they were required to identify themselves by shouting, “Unclean! Unclean!” so that others could clear out and avoid any contact with them (Leviticus 13:45). Lepers had to resort to begging, relying on the mercy of others to spare them food and other daily necessities. The impurity of leprosy is like sin in that it isolates us from our communities, separates us from God, and eventually leads to death. And this is why Jesus’ approach to the outcast lepers in His day was so startling. He didn’t turn away from them, He didn’t clear out of the way, and He didn’t draw back in horror or disdain; He reached out His hand and touched them. And instead of their leprosy making Jesus unclean, His holiness overcame their impurity and made them clean (Matthew 8:1–4; Luke 17:11–16). Jesus’ power is such that He can rid us of all impurity: physical, moral, and spiritual.
When we think of impurity, we often think of sexual sin. Sexual immorality is certainly included in the Bible’s idea of impurity, but there is more to it than that. Impurity really includes all kinds of sin and encompasses any activity, thought, word, or action that does not conform to God’s will for our lives. “God did not call us to be impure, but to live a holy life” (1 Thessalonians 4:7).
The Bible teaches that impurity is the default state for human beings, post-fall. We are all born as unclean sinners (Psalm 51:5; Romans 3:23), and we must be cleansed if we are to see God. No one but God is perfect; all of us have been polluted through the impurity of sin. The slightest sin is still a lethal contaminant in our souls, and this is bad news for us: “Of this you can be sure: No immoral, impure or greedy person . . . has any inheritance in the kingdom of Christ and of God” (Ephesians 5:5; cf. Revelation 21:27). Like lepers, we are all in desperate need of God’s mercy and grace to reach out and cleanse us from the impurities that defile us. We need Jesus’ touch and the gift of His righteousness (1 Corinthians 1:30). “Blessed is the one whose sin the LORD does not count against them” (Psalm 32:2).
The glory of the gospel is that God can make what is impure, pure; and what is unclean, clean. To our eternal joy, God desires to do just that, for Christ’s sake: “If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness” (1 John 1:9).