Leviticus 14 - The first half of this chapter deals with the cleansing of one who had an infectious skin disease. Also the sacrificial offerings the healed person is to make to the Lord. This offering would be a source of worship and thanksgiving for the healing that God provided. When the Israelites come into the Promised Land and begin to reside in the houses of the land they may find what appears to be mildew in the walls. They are to ask the priest to come and examine the house. Note, they are to remove the household furnishings before the examination so that nothing left in the house is considered unclean. The priest will order some repairs to be made if mildew is found, but if the house shows the mildew is spreading through the house then the house is to be destroyed. God wants His people to live clean lives and to dwell in clean houses.
Leviticus 15 - In verse 31 God explains why these instructions for cleansing are important. He is a perfectly holy God and He wants His people to be pure from all kinds of disease or uncleanness. In this chapter both the usual and unusual discharges from a person's body make them unclean and in need of cleansing. It is similar to our getting dirty and cleaning up thoroughly. It was understood that a person needed to watch out for moral impurity in their lives that could defile others as well. This is still a good principle to follow today - keep your heart clean as you seek to keep your body clean.