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31 And God saw every thing that he had made, and, behold, it was very good. And the evening and the morning were the sixth day.
To be fruitful relates to goodnesses, and to be multiplied, truths.
(References: Arcana Coelestia 1014, 1018)
16 The day is thine, the night also is thine: thou hast prepared the light and the sun.