This parashah, and the following one, defines the situations and physical manifestations that render a person ritually impure. It is extremely difficult to find the common denominator among all the cases described. The woman who has given birth, or is in her menstrual period, or any bloody flow that repeatedly issues from her womb, makes her impure. Every seminal flow that comes from a man makes him impure. Both men and women who suffer from certain skin diseases are also considered impure. In all cases, by means of a ritual directed by a priest, they are able to return to a state of purity.
According to a Talmudic commentary (Yoma 67,b), these standards are Chukot, divine decrees that are absolutely incomprehensible to human beings, which, as with some others commands, are Satan’s way to confuse the Jewish people.
However, other sages from long ago tried to find a rational explanation for these norms. From Talmudic times, epidermal diseases were attributed to improper behavior. Rabbi Shmuel Ben Nachmani (Arakhin 16, a) explains that seven transgressions can cause the appearance of tzaraat, leprosy, in someone. One of them is defaming a person. The one afflicted by it is called metzora, a word that is interpreted as an acrostic of its letters: Motzi Shem Ra, the one who slanders.
Beyond the many explanations, underlying these chapters is the biblical vision of the human being as a psychophysical unity. Psychic disorders alter physical health and vice versa, a fact that modern science tests and affirms with more studies day by day.