“The symptoms that led to a verdict of uncleanness were as follows. The “skin disease” had to be long and lasting. It had to be old (Lev 13:11) or last at least a week or two (Lev 13:4, Lev 13:26, Lev 13:33, Lev 13:50). It had to be deeper than the skin (Lev 13:3, Lev 13:20, Lev 13:25, Lev 13:30) or irremovable by washing (Lev 13:55). It was something that affected only part of a person. It was patchy. If it covered the whole body, it did not defile (Lev 13:12-13). With garments and articles, it is clear that only part of the object was affected, since Lev 13:56 speaks of tearing out the affected spot.”
New International Commentary – Old Testament
We may wonder, why was the partial covering considered unclean but the full covering was not? Most scholars believe that when the disease fully covered the person, it was no longer in the contagious phase.
The aim of these laws was not to ostracize people but to protect the larger community from spreading infection. It is actually very similar to how we ask people to wear masks during a viral outbreak.
Obviously, there was a spiritual lesson as well. The disease is a vivid analogy for how sin can slowly infect every aspect of our body (and eventually the larger community). When considering this idea, it is amazing to reflect on the life of Jesus and His direct association with such people.
Though we would have expected Jesus to shy away from what was considered “unclean,” He actually came to seek and cleanse those very people. He came to confront the full potency of our sin. He did not come to save the righteous, but sinners just like you and I. Whatever the severity of your “filth,” Jesus would never turn you away. This is our Savior!