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16 And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.
To be fruitful relates to goodnesses, and to be multiplied, truths.
(References: Arcana Coelestia 1014, 1018)
7 And you, be ye fruitful, and multiply; bring forth abundantly in the earth, and multiply therein.