Tazria: Chapter 26
"And be holy"

We learn here of the proper time for mating for those who study the Torah, and that is midnight on Shabbat when God walks with the righteous in the Garden of Eden. People are holy only by association with their God; if they draw away from Him they lose their holiness and draw upon themselves souls from the side of the Evil Inclination. The priest can recognize people's sins by the blemishes that show when they come from the Other Side.