This parashah describes the impure animal species that are forbidden to eat. It sets the basis for what is known by the word Kashrut, the fitness of a food to be consumed by a Jew.
There are many explanations for these food standards. The Torah itself (Lev. 11:43-45) explicitly states that the enumerated species are impure and so contaminate those who eat them. This would distance the Jew from the dimension of holiness for which he was taken by God out of the land of Egypt.
Maimonides understood these dietary norms as defining proper nutrition and that medicine would confirm this (Moreh Nevukhim, III, chap. 48). Nachmanides held that the prohibitions found in Lev. 11:13, which ban the eating of predatory animals, prevented animal aggressiveness from being transferred into humans.
In Midrash Tehillim (146.4) is a surprising statement: at first all the species were pure and they will be so again in the world to come. Why, then, did God forbid them? The midrash answers: to see who fulfills God’s precepts and who does not.
The Midrash suggests that these rules are meant to teach people that not everything is allowed, that there are limits that they must learn to incorporate into their beings.
The last verse of the parashah says that one must learn to differentiate pure animals from the impure, an exercise that should lead the individual to make distinctions in all aspects of life: between good and bad, justice and injustice, mercy and the malice. It seems that this is the ultimate intention of Kashrut.