זוהר שמות — דף קסה ע”א

The ten curtains of the Tabernacle correspond to the ten heavens, a secret of secrets transmitted only to those who know wisdom. Seven heavens above mirror seven below, and the seventh is the most exalted of all. The heaven called Aravot is the seventh, combining fire and water together and blending both sides, and upon it the Holy One, blessed be He, rides. The High Priest who entered before it entered only with joy, for this heaven is entirely joy and contains no sadness whatsoever.