NOTES for Lev 15:1-33
The norms connected with "discharges" are today one of the foundations of kashrut in Judaism, especially for women. It may be noted, incidentally, that in Judaism the norms concerning these "discharges" became stricter over the centuries, and especially for women, although originally even an ordinary runny nose could be understood as a "discharge," and in that interpretation the corresponding prescriptions applied to men to a degree not much less than to women. The point is that in ancient times every "discharge" was considered a sign of illness, regardless of its origin.
Illness, in turn, was connected with a reduction of that fullness of life which was considered a necessary condition for sanctification. Especially visible testimony to such a reduction was precisely every kind of "discharge": a person visibly lost strength, lost his wholeness literally in a physical way, and was turned into nothing, at least in part. No fullness of life was compatible with such a state.
Meanwhile, this fullness was absolutely necessary for sanctification: what was sanctified was precisely a person's life, his vital force, that stream of life which in the Bible is called a "living soul." In antiquity and in other periods, people often sanctified springs, brooks, and rivers, for example, but it would hardly have occurred to anyone to sanctify a puddle, a swamp, or a stream of dirty water. In the times when the Book of Leviticus was written, people assumed that every illness turns the stream of a person's life from a clean river into something like a drainage ditch.
Of course, no one ever regarded illness or "discharges" as sin, but defilement could be connected not only with sin. Everything that diminished the fullness of life in a person or polluted its stream defiled. The person might not be guilty of this; he could be guilty only when the cause of defilement was a sin he had committed. But the fact remained: the fullness of life disappeared, and its stream was polluted. Therefore the sanctification of such a polluted stream was impossible.
There was no catastrophe here: purification rituals had been developed precisely for such cases. If the defilement was not connected with sin, naturally no one expected repentance from the person and no one accused him of anything. He simply had to be purified, as one needs to wash after dirty work or after accidentally falling into mud. For us today, living in the age of the approaching Kingdom, whose breath washes away any dirt and makes life full, this is hard to understand; but for people of pre-Christian times, everything said here was completely real and urgent.