זוהר שמות — דף קפז ע”א

During the festival of Sukkot, the seven holy days require feeding the ministering angels of the nations. The lower world must sustain these nations at the hour when the Moon rejoices with her husband, so that they do not disturb her joy. Sukkot is written deficiently, indicating that this lower world is incomplete. The seventy-two sacrifices correspond to the seventy nations, and the eighth day, Shemini Atzeret, is the culmination of all the days.