Arcana Coelestia #61
61. Everything that has to do with cognitions of faith is called spiritual, and everything that has to do with love to the Lord and towards the neighbour is called celestial. The former belong to man's understanding, the latter to his will.
Genesis 1:6-8
6
And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.
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.
8
And God called the firmament Heaven. And the evening and the morning were the second day.