Verse 1-17 — The plague of leprosy was an uncleanness, rather than a disease. Christ is said to cleanse lepers, not to cure them. Common as the leprosy was among the Hebrews, during and after their residence in Egypt, we have no reason to believe that it was known among them before. Their distressed state and employment in that land must have rendered them liable to disease. But it was a plague often inflicted immediately by the hand of God. Miriam's leprosy, and Gehazi's, and king Uzziah's, were punishments of particular sins; no marvel there was care taken to distinguish it from a common distemper. The judgment of it was referred to the priests. And it was a figure of the moral pollutions of men's minds by sin, which is the leprosy of the soul, defiling to the conscience, and from which Christ alone can cleanse. The priest could only convict the leper, (by the law is the knowledge of sin,) but Christ can cure the sinner, he can take away sin. It is a work of great importance, but of great difficulty, to judge of our spiritual state. We all have cause to suspect ourselves, being conscious of sores and spots; but whether clean or unclean is the question. As there were certain marks by which to know it was leprosy, so there are marks of such as are in the gall of bitterness. The priest must take time in making his judgment. This teaches all, both ministers and people, not to be hasty in censures, nor to judge anything before the time. If some men's sins go before unto judgment, the sins of others follow after, and so do men's good works. If the person suspected were found to be clean, yet he must wash his clothes, because there had been ground for the suspicion. We have need to be washed in the blood of Christ from our spots, though not leprosy spots; for who can say, I am pure from sin?
Verse 18-44 — The priest is told what judgment to make, if there were any appearance of a leprosy in old sores; and such is the danger of those who having escaped the pollutions of the world are again entangled therein. Or, in a burn by accident, ver.24. The burning of strife and contention often occasions the rising and breaking out of that corruption, which proves that men are unclean. Human life lies exposed to many grievances. With what troops of diseases are we beset on every side; and thy all entered by sin! If the constitution be healthy, and the body lively and easy, we are bound to glorify God with our bodies. Particular note was taken of the leprosy, if in the head. If the leprosy of sin has seized the head; if the judgment be corrupted, and wicked principles, which support wicked practices, are embraced, it is utter uncleanness, from which few are cleansed. Soundness in the faith keeps leprosy from the head.
Verse 45,46 — When the priest had pronounced the leper unclean, it put a stop to his business in the world, cut him off from his friends and relations, and ruined all the comfort he could have in the world. He must humble himself under the mighty hand of God, not insisting upon his cleanness, when the priest had pronounced him unclean, but accepting the punishment. Thus must we take to ourselves the shame that belongs to us, and with broken hearts call ourselves "Unclean, unclean;" heart unclean, life unclean; unclean by original corruption, unclean by actual transgression; unclean, therefore deserving to be for ever shut out from communion with God, and all hope of happiness in him; unclean, therefore undone, if infinite mercy do not interpose. The leper must warn others to take heed of coming near him. He must then be shut out of the camp, and afterward, when they came to Canaan, be shut out of the city, town, or village where he lived, and dwell with none but those that were lepers like himself. This typified the purity which ought to be in the gospel church.
Verse 47-59 — The garment suspected to be tainted with leprosy was not to be burned immediately. If, upon search, it was found that there was a leprous spot, it must be burned, or at least that part of it. If it proved to be free, it must be washed, and then might be used. This also sets forth the great evil there is in sin. It not only defiles the sinner's conscience, but it brings a stain upon all he has and all that he does. And those who make their clothes servants to their pride and lust, may see them thereby tainted with leprosy. But the robes of righteousness never fret, nor are moth-eaten.