As part of their covenant with the Lord, the Israelites were given regulations concerning what is considered clean and unclean. At times this is a means of health and well-being, at other times it serves as a distinction from surrounding nations. The term “unclean” doesn’t necessarily mean those things are dirty, germ-infested, or immoral, though some of them certainly are, but these things are all ceremonially unclean; this is how Israel is to be set-apart from other nations, and given fully to the Lord. These regulations would have made Israel a distinct people on the earth, and the nations would know by their actions that they were fully devoted to the Lord.