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7 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
'A sandal tree' signifies aspects of the natural self.
(Referencias: Apocalypse Explained 518)
18 I will open rivers on the bare heights, and springs in the midst of the valleys. I will make the wilderness a pool of water, and the dry land springs of water.