The old sage speaks about the reason that God led Yisrael into the powerful wilderness, the domain of Samael, when they left Egypt. Had they not sinned, God would have crushed Samael so he would have had no power, but because they sinned they spent forty years in the wilderness to fulfill the verse, "And you shall bruise his heel." We are told that the only light is that light which comes out of the darkness. There is no service of God except from out of darkness, and no good except from out of evil. Overall perfection is good and evil together that rise to the good afterward.