The first mention of leprosy in historical documents was about 1500 BC. The Bible mentions it as early as the book of Leviticus where its description and treatment are listed in chapters 13 and 14. As the centuries progressed, most doctors considered leprosy a genetic disease. Finally on February 28, 1873, Dr. Gerhard Henrik Armauer Hansen of Sweden discovered the bacillus that caused leprosy, proving once and for all that it was indeed an infectious disease, and eventually giving his name to it: Hansen’s disease. The Bible seemed to realize from the beginning that it was infectious.
A leper was considered ceremonially “unclean,” Lev 13:46. That means he was no longer fit to even stand before God, much less serve Him. If he were a priest, he could not partake of the sacrifices, Lev 22:4. But no matter who he was, he was banned from the Temple, 2 Chron 26:21, and expelled from the people because his mere presence defiled the entire group, Num 5:2,3.
He lived in isolation with others who shared his doom, and was required to warn anyone who might come near him with the shout of, “Unclean! Unclean!” He had to make his disease obvious by his appearance, wearing torn clothes and leaving his hair loose and disheveled, with his upper lip covered, Lev 13:45.
Leprosy became a metaphor for sin in the Bible, as should be obvious from the verses cited above and their spiritual significance-not fit to serve God, not fit to enter into His presence, not fit to be with His people, in fact, one who would defile the whole people. God sent leprosy as a punishment several times—on Miriam, on Gehazi, on King Azariah/Uzziah. The progress of the physical disease begins with an invisible infection, leading to disfigurement, deterioration, and death. Surely you can see the progress of sin in a person’s life in parallel.
And that leaves us with two profound lessons. First, for Jesus to actually touch a leper and heal Him showed not only his power but also his mercy. And Jesus is the only one who can cure us of that disease called sin. He was the one who loved us enough to come down among all of us spiritual lepers, regardless of the danger of infection, and make us clean. How many of us are like the nine lepers instead of the Samaritan, who was so profoundly grateful for being cleansed that he would fall on his face in gratitude to the one who cleansed him, even if it delayed his symbolic entrance back into the fold?
And second, we should view sin as we view that awful disease. Too many times I see Christians who flock to other diseased (sinful) people, heedless of the risk of infection, in fact, hoping for it, rather than treating it like the life-endangering disease it is. Yes, we need to serve the sinners--by leading them home to the Great Physician, not by trying on their clothes, eating from their bowls, and rolling around in their beds. Sin, like leprosy, will make us outcasts from God, the only source of a cure. Don’t we realize that, or is it that we long to be lepers like the rest of the world?
And behold, a leper came to him and knelt before him, saying, “Lord, if you will, you can make me clean.” And Jesus stretched out his hand and touched him, saying, “I will; be clean.” And immediately his leprosy was cleansed, Matt 8:2-3.