זוהר שמות — דף קל ע”א

The evening prayer was instituted as optional because the Other Side dominates the night and darkens the light. At evening, the fats and sacrificial portions burned on the altar nourish the bands of impure forces that go out and rule at night. The altar smoke would rise through the northern opening, where evil spirits dwell, feeding them so they would not go out to rule over the Holy Land. A minister named Sangirya and sixty thousand myriads of camps would receive the smoke at the northern opening. These forces roam at night, tempting souls and causing impurity.