Leviticus gives an explicit theological reason for the entire classification, stated at the end of chapter 11 rather than left implicit: "for I am Jehovah your God; sanctify yourselves therefore, and be ye holy; for I am holy... for I am Jehovah that brought you up out of the land of Egypt, to be your God; ye shall therefore be holy, for I am holy." The dietary boundary is presented as an extension of a broader logic of separation running through the priestly legislation, in which Israel's holiness, its being set apart, is expressed not only through ritual and sacrifice but through the ordinary daily act of eating, so that a meal itself becomes a recurring, physical enactment of the community's distinct identity rather than a purely practical matter of nutrition or food safety.
Later rabbinic tradition, elaborating these biblical rules into the fuller system known as kashrut, developed extensive additional case law, much of it collected in the Mishnah's tractate Hullin, addressing questions the biblical text leaves open, how an otherwise permitted animal must be slaughtered, how meat and milk must be kept separate, and how to classify creatures whose status under the original criteria is ambiguous. What the biblical text itself makes clear, and what later elaboration never abandoned, is that the categories tahor and tamei describe fitness for a holy people's table rather than a claim about which animals are inherently good or evil, dangerous or safe, a distinction the text is careful to keep separate from ordinary ideas of cleanliness.