When the Jewish people entered Canaan God began to work with His people in purifying them from their sins. Leprosy came onto their homes that they possessed and it brought about terrible problems. Most scholars believe that the "leprosy" described in Leviticus 14:33-57 is not the leprosy we often identify with. More than likely it was a mildew that coated the walls of the homes and infected both cloths and skin. But in order to teach the people what was going on the Lord in His sovereignty "put a mark of leprosy on the house in the land of your possession" (v. 33).
The people were to share the problem with their priests who would see the mark and then make a sacrificial atonement. The house would be considered "unclean" (v. 44) and "quarantined, and unclean until evening" (v. 45). "Two birds" would be used in the sacrifice. One was to be killed and the other released (vv. 51-53). The one slain represents the atonement and the one released shows that their sin (of leprosy) was removed from their presence! The priest "shall make atonement for the house, and it shall be clean" (v. 53). The people could be infected by the leprosy. They could develop scales, swellings, scabs, or bright spots on their skin (vv. 54-55). Both their houses and their garments were infected.
God was giving them spiritual lessons by the sacrifice of the birds "to teach [them] when they are unclean, and when they are clean. This is the law of leprosy" (v. 57). The Lord used many lessons such as this to give blessings to His people that no other nation had!
--Dr. Mal Couch