Having discussed whether animals are pure or impure, whether they are kosher to eat or not, the Torah now turns to discuss the purity and impurity of human beings.
Yet there is a fundamental difference between the purity or impurity of man vs. animal. An animal is either kosher, or not — its state is determined from birth. And when it dies, a kosher animal becomes impure if it was not slaughtered correctly — meaning that only human intervention prevents it from becoming impure. In both life and death, an animal does not change its own state. A human being, on the other hand, can become pure or impure repeatedly throughout his or her lifetime.
This distinction between the purity of animals versus human beings is parallel to the fundamental difference in our natures. An animal is a creature of instinct; it performs the mission that G-d gave it without conscious thought. Only human beings get to choose how to behave, which is both a blessing and a curse.
A human being combines a physical body and a Divine soul, and repeatedly chooses which nature to follow. We can attach ourselves to the Divine, or (ch”v) pursue our base instincts. In death the body and soul separate — the purity of the soul leaves the impurity of the body. As a result, the corpse reflects the deepest level of impurity. Not only physical contact, but even traveling over a grave or sharing a room with a body is sufficient to make a person impure.
Throughout our lives, we, unlike the animals, can choose to make ourselves more G-dly and pure. May we always make the right choices!