The Diagnosis of Defilement Text: Leviticus 13:1-8
Introduction: God's Audiovisual Aids
We come now to the book of Leviticus, and to a chapter that many modern Christians, if they are being honest, would prefer to skim. We find here detailed statutes concerning skin diseases, mold, and mildew. It can feel alien, meticulous to the point of being tedious, and frankly, a bit unspiritual. But if we think this way, we are making a catastrophic mistake. We are treating God's Word like a buffet, picking out the parts we find immediately palatable and leaving the rest to congeal on the steam table. All Scripture is God-breathed and profitable, and that includes the diagnostic criteria for leprosy.
The ceremonial law of the Old Testament was a massive, acted-out audiovisual aid. It was a picture book for a people who were learning the grammar of holiness. God was teaching Israel, and us through them, the fundamental distinction between clean and unclean, holy and common, life and death. These laws were not arbitrary. They were shadows, and the substance is Christ. Leprosy, in the Old Testament, was not simply a medical problem; it was a profound theological statement. It was a living, walking parable of sin.
Sin is not just a mistake or a poor choice. It is a defilement. It is a spiritual contagion that isolates us from the presence of a holy God and from His holy people. And just as the leprous man was put outside the camp, the unrepentant sinner, in the New Covenant, is to be put outside the church. The principles laid out here in Leviticus 13 are not obsolete; they are transfigured. The role of the priest in diagnosing the disease is now the role of the elders in the church, who must guard the health and holiness of the flock. The careful process of examination, waiting, and judgment is a direct pattern for church discipline. If we want to understand sin, holiness, the church, and the gospel, we must pay close attention to these statutes about leprosy.
The Text
Then Yahweh spoke to Moses and to Aaron, saying, "When a man has on the skin of his body a swelling or a scab or a bright spot, and it becomes an infection of leprosy on the skin of his body, then he shall be brought to Aaron the priest or to one of his sons the priests. Then the priest shall look at the mark on the skin of the body, and if the hair in the infection has turned white and the infection appears to be deeper than the skin of his body, it is an infection of leprosy; when the priest has looked at him, he shall pronounce him unclean. But if the bright spot is white on the skin of his body, and it does not appear to be deeper than the skin, and the hair on it has not turned white, then the priest shall isolate him who has the infection for seven days. Then the priest shall look at him on the seventh day, and if in his eyes the infection has not changed and the infection has not spread on the skin, then the priest shall isolate him for seven more days. And the priest shall look at him again on the seventh day, and if the infection has faded and the mark has not spread on the skin, then the priest shall pronounce him clean; it is only a scab. And he shall wash his clothes and be clean. But if the scab spreads farther on the skin after he has shown himself to the priest for his cleansing, he shall appear again to the priest. And the priest shall look, and if the scab has spread on the skin, then the priest shall pronounce him unclean; it is leprosy."
(Leviticus 13:1-8 LSB)
The Presentation of the Problem (v. 1-2)
The instruction begins with God speaking directly to His appointed leaders.
"Then Yahweh spoke to Moses and to Aaron, saying, 'When a man has on the skin of his body a swelling or a scab or a bright spot, and it becomes an infection of leprosy on the skin of his body, then he shall be brought to Aaron the priest or to one of his sons the priests.'" (Leviticus 13:1-2)
Notice first that this is a matter of divine revelation. God Himself establishes the protocol. The diagnosis of spiritual defilement is not left to popular opinion, personal feelings, or a democratic vote. God sets the standard. Moses, the lawgiver, and Aaron, the high priest, receive the instruction. This is a matter for the civil and the ceremonial leadership of the people. The health of the covenant community is everyone's concern, but the official diagnosis is the responsibility of the priests.
The problem begins on an individual: "a man." Sin is personal. It manifests in the lives of individual people. It appears as a "swelling or a scab or a bright spot." Sin often begins as something that seems minor, an anomaly on the surface. But it has the potential to become an "infection of leprosy," a defiling contagion. The word for leprosy here, tsaraath, covers a range of skin diseases, but its significance is ceremonial, not just medical. It represents a condition that makes one unfit to dwell in the camp, where God's holy presence resides.
And what is the prescribed action? The man "shall be brought to Aaron the priest." He doesn't diagnose himself. His family doesn't hide him in the tent. The issue must be brought into the light and submitted to the proper authority. This is the first step of any kind of church discipline. When a potential sin-infection appears in the body, it must be brought to the elders of the church. Hiding it, ignoring it, or pretending it's not there is the surest way to guarantee that it spreads.
The Priestly Examination (v. 3-4)
The priest's role is not to heal, but to look. He is a diagnostician, a guardian of the camp's purity.
"Then the priest shall look at the mark... and if the hair in the infection has turned white and the infection appears to be deeper than the skin of his body, it is an infection of leprosy; when the priest has looked at him, he shall pronounce him unclean. But if the bright spot is white on the skin of his body, and it does not appear to be deeper than the skin, and the hair on it has not turned white, then the priest shall isolate him who has the infection for seven days." (Leviticus 13:3-4)
The priest is given two clear diagnostic criteria for an immediate declaration of uncleanness. First, has the hair in the affected area turned white? This signifies that the disease has changed the very nature of the man's body. Second, does the infection appear "deeper than the skin"? This is crucial. Sin is never just a surface-level problem. True spiritual leprosy, deep-seated sin, is not just a skin-deep blemish. It goes to the heart. If these two signs are present, the priest's duty is clear and immediate: "he shall pronounce him unclean." This is a declarative act. The priest does not make him unclean; he authoritatively declares what is already true before God.
But what if the case is ambiguous? What if the spot is there, but it is superficial? If it is not deep and the hair has not turned white, the priest does not immediately dismiss it. He also does not immediately condemn. He waits. He "shall isolate him... for seven days." This is a period of quarantine and observation. This is a picture of wisdom and patience. Church elders are not to be hasty. When a matter of sin is brought to them, they must investigate carefully. They must not be quick to pronounce judgment, nor should they be quick to dismiss a potentially serious issue. They must take the time to watch and see what the "infection" does.
The Period of Waiting and Re-examination (v. 5-6)
Patience and careful observation are central to the process. The standard is not a feeling or a hunch; it is the objective evidence.
"Then the priest shall look at him on the seventh day, and if in his eyes the infection has not changed and the infection has not spread on the skin, then the priest shall isolate him for seven more days. And the priest shall look at him again on the seventh day, and if the infection has faded and the mark has not spread on the skin, then the priest shall pronounce him clean; it is only a scab. And he shall wash his clothes and be clean." (Leviticus 13:5-6)
After the first week, the priest looks again. The key question is whether the infection is active. Has it spread? If it is static, "at a stay," then more observation is needed. He is isolated for another seven days. This shows us that some spiritual conditions require time to properly diagnose. Not every problem is a five-alarm fire. Some require patient oversight.
After the second week, the priest examines him a final time. If the infection has faded and has not spread, the priest can make a different declaration: "he shall pronounce him clean." It was not leprosy after all; it was "only a scab." It was a surface wound, a blemish that healed. The man is then to wash his clothes and is restored to the community. This is a beautiful picture of what happens when a brother is confronted about a potential sin, and it is found to be a misunderstanding, or a minor offense that he quickly repents of. He is declared clean, he takes the simple steps of purification, and fellowship is restored. The goal of church discipline is not to kick people out, but to declare them clean whenever biblically possible.
The Spreading Scab (v. 7-8)
But the final verses of our text show the other possible outcome, and it is a grim one.
"But if the scab spreads farther on the skin after he has shown himself to the priest for his cleansing, he shall appear again to the priest. And the priest shall look, and if the scab has spread on the skin, then the priest shall pronounce him unclean; it is leprosy." (Leviticus 13:7-8)
Here we see the definitive sign of true leprosy: it spreads. Even something that was initially judged to be "only a scab" can reveal its true nature over time. The man had been pronounced clean, but the contagion was still latent within him. This is a picture of false or incomplete repentance. It is the person who says all the right words, who goes through the motions, but whose heart has not been changed. The sin was not dealt with, and so it inevitably breaks out again, and it spreads.
When this happens, the priest's duty is once again clear and non-negotiable. He must look, see the evidence of the spreading corruption, and "pronounce him unclean; it is leprosy." The time for waiting is over. The disease has declared itself. This is the point in church discipline where, after repeated warnings and patient waiting, a person's continued and unrepentant sin makes it plain that they are a danger to the health of the body. The elders have no choice but to declare what is true and excommunicate them, putting them outside the camp for the sake of the purity of the church and, prayerfully, for the ultimate salvation of the sinner.
Our Great High Priest
This entire process, with its priests and examinations and declarations, can seem quite harsh to our modern, sentimental ears. But it is a profound mercy. It shows us that God takes holiness seriously, and He takes sin seriously because of the destruction it brings. This whole chapter is designed to make us long for a cure.
And that is the point. We are all born with leprosy. We are born with sin that is "deeper than the skin." It is in our hearts, our very nature is corrupted, and it spreads throughout our entire lives, defiling everything we do. We are all, by nature, unclean. We deserve to be cast out of the presence of God forever.
The priests in Leviticus could only diagnose the problem. They could declare a man unclean, but they could not make him clean. They could pronounce a man clean if his disease healed on its own, but they had no power to heal it. They could only inspect and isolate.
But we have a Great High Priest, the Lord Jesus Christ. He is not afraid of our uncleanness. When the lepers came to Him, He did not shrink back. He did not call for an examination. He reached out His hand and He touched them. The clean touched the unclean, and instead of the clean becoming defiled, the unclean became clean. He did not just declare them clean; He made them clean. "I am willing," He said, "be cleansed" (Mark 1:41).
On the cross, Jesus took all of our spiritual leprosy upon Himself. He became unclean for us. He was cast outside the camp, outside the city gates, bearing our reproach. He was isolated in the darkness so that we could be brought into the light. And through His resurrection, He offers not just a diagnosis, but a radical cure. He does not just cover over our scab; He gives us a new heart. He washes us, not just our clothes, but our very souls in His own blood. And He declares us clean, once and for all, not based on our performance or the fading of our spots, but based on His perfect, finished work.