And if any man’s seed (semen) of copulation go out from him, then he shall wash all his flesh in (the sexual) waters (of Yesod), and be unclean until the even (Klipoth). The woman also with whom man shall lie with seed (semen) of copulation, they shall both bathe themselves in (the sexual) waters (of Yesod), and be unclean until the even (Klipoth).
This was a law given to the Levites (priests). The priesthood is how we are following the path of God. It was written for those who start the path. It was written by the initiates for the initiates – it is sad how everyone has a Bible in their home but few comprehend it, because it was written for those who are working in the Self-realization of the Being.