First let's lay a little ground work. Please read: Leviticus Chapters 13 and 14.
In most English versions of the Bible the Hebrew word, tzaraat, is translated as leprosy. However, this is not a correct translation of this skin disease at all. This is a mistranslation of the Hebrew word. The Hebrew word, tzaraat, was not translated into leprosy until around the middle ages when it was translated into Arabic as lepra and then into Greek as leprosy. Actually the Hebrew word does not compare to our modern disease known as leprosy, or Hansen's disease, as we shall see.
Rabbi's have understood and taught for centuries about the origins of tzaraat. Tzaraat was mysterious because it not only affected a person's skin, but could also infect garments,belongings, and houses. Instead of requiring medical attention from a physician, it required examination from the priest. Interestingly, if the skin plague had COVERED the entire body, the person was declared CLEAN, NOT UNCLEAN.
The disease manifested itself as a swelling, scabs, or white spots. If a person thought that he/she had the beginnings of the disease then he/she was immediately to go to a priest at which time they would be examined. After ONE WEEK they would be checked again by the priest to see if the disease had spread. Hansen's disease spreads much slower than this and you definitely would not be free from Hansen's disease if it covered the entire body.
The treatment for the disease was total social isolation from the rest of the community. They had to live totally separated and cry out, “unclean, unclean” if anyone approached them. Talk about social anxiety!
So what is the mysterious skin affliction? Well, the Rabbi's teach that it is not a physical, medical, problem but a spiritual problem. They teach that the disease is brought upon a person because of sin. It is a warning from Elohim that they need to mend their ways. The Rabbi's teach that the sins most likely to have caused this condition were anti-social sins such as: gossip, murder, sexual immorality, pride, perjury, arrogance, envy. They specifically focused on evil speaking or derogatory speech, against another; in Hebrew this is called lashon hara, “evil tongue”.
Examples that correlate with this understanding can be found in the case with Miriam, see Numbers 12. Miriam was afflicted with this skin condition because she spoke against Moses. Though Moses and Aaron pled for her to be healed immediately, she still had to be separated from the community for seven days.
Other Biblical examples can be found in Leviticus 13-14, II Kings 5:1, II Kings 7:3-10, II Kings 15:5, II Chronicles 16:20-23.
Lashon Hara is a very serious offense against another person and God does not take it lightly. See Leviticus 19:16, James 4:11, Matthew 12: 35-36, Proverbs 6:16-19.
In Matthew 15:16-20, Yeshua stated the following:
“And Jesus said, Are ye also yet without understanding? Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught? But those things which proceed out of the mouth come forth from the heart; and they defile the man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
These are the things which defile a man: but to eat with unwashen hands defileth not a man.”
It would seem by His statement that He was in agreement with the teaching that these things cause a person to be unclean. In Tabernacle/Temple days would they have caused a person to break out with tzaraat? Chances are yes!
Some ancient Jewish writers saw tzaraat as a removal of godliness. For example, if a person saw tzaraat beginning in his house then they knew that God was removing His presence from their home. They knew that they had done something of which they needed to repent.
How was it that if a person was totally covered in the skin affliction that they were made CLEAN? It is easy for a person to make excuses for a little sin, in this case a little scab perhaps, but only after a person has totally given over to their sinful state and experienced the isolation from God and the community that it brings, do they realize that they need a redeemer. They are now ready to be made clean and whole; with repentance.
Wouldn't it be nice if God gave us such a warning today when we had committed a sin? If He said to us by an affliction that we had sinned and needed to repent? Well, remember that scripture bears out that curses come upon us by our own disobedience. Remember the story of Balak and Baalam? Baalam couldn't curse the children of Israel because they were obedient, but he told Balak how to make them curse themselves. If Balak could cause them to be disobedient then they would bring curses upon themselves. Well, that's just what happened! Point being: we need to guard ourselves from the enemy who seeks to kill, steal and destroy by any means necessary.