The calf
We learn that the golden calf gave the spirit of unholiness a place of focus in which it could strengthen. Furthermore, even though the children of Yisrael had been free of death from the time they stood upon Mount Sinai they now brought death upon themselves and upon all future generations. We are told that Aaron had to be purified for seven days because if it were not for him the golden calf would not have existed. Rabbi Shimon says that the golden calf is from the left side. The children of Yisrael had drawn upon itself the Evil Inclination with their worship of the calf, and when they wanted to become purified again they had to offer a goat, the goat being a part of the Evil Inclination. Next we are told that when the calf was made, as in: "I threw it into the fire, and there came out this calf," it was made by sorcerers. Rabbi Shimon tells us of successful and unsuccessful sorcerers, some men are fit for sorcery and some are not. In the event of the creation of the golden calf, everything that was necessary for the spirit of defilement was ready and waiting: a completely wasted desert, enough gold, and Aaron who was willing to sin in this way. Everything was ready for the Other Side, and the deed was done. When Aaron was ready to be redeemed he offered a calf on the altar, thus executing judgment and subduing the rulers of the Other Side.