And God blessed them, and God said to them, “Reproduce and multiply, and fill the earth and harness it, and rule over the fish of the sea and over the bird in the heavens and over every living animal creeping on the earth.”
The earliest people called the interconnection of understanding and will or of faith and love a marriage, so the generation of any good from that marriage they termed reproduction, and the generation of any truth they termed multiplication. Because they did so, the prophets did so too; in Ezekiel, for instance:
I will multiply human and animal upon you, [mountains of Israel,] and they will multiply and reproduce; and I will cause you to live as in your ancient times. And I will do good to you beyond that at your beginnings, and you will know that I am Jehovah. And I will cause humankind—my people Israel—to walk upon you. (Ezekiel 36:8, 9, 10, 11, 12)
Humankind here means the spiritual being, which is also called Israel; the ancient times mean the very earliest church; and the beginnings mean the ancient church, which followed the Flood. The multiplying (of truth) comes before the reproducing (of good) because these verses describe the person who is being reborn, not the one who has been reborn already.
When the understanding couples with the will in us, or faith with love, the Lord through Isaiah calls us a married land:
No longer will your land be named Devastated; but you will be called I Am Well Pleased with Her, and your land, Married, since Jehovah will take pleasure in you. And your land will be married. (Isaiah 62:4)
The fruits of truth produced by this marriage are called sons, while the fruits of goodness are called daughters, as occurs quite often in the Word.
The earth is filled when truth and goodness proliferate, because when the Lord blesses and says things (that is, operates), goodness and truth grow beyond measure. As he states:
The kingdom of the heavens is like a mustard seed that you have taken and sown in your field, which to be sure is the smallest of all the seeds; but when it has grown, it is bigger than all the plants and becomes a tree, so that the birds of the sky come and nest in its branches. (Matthew 13:31, 32)
The mustard seed is the good we have before developing a spiritual orientation; it is the smallest of all the seeds, because we suppose that we do good on our own. Anything we do on our own is evil through and through, but since we are engaged in the process of being reborn, we have a trace—the smallest possible trace—of goodness. Later, as faith becomes more closely connected with love, it grows larger—a plant. When the connection is completed, it turns into a tree, and then the birds of the heavens (which here as before are true ideas, or the contents of the understanding) nest in its branches (the facts we know).
When we are spiritual people or are becoming spiritual, we are subject to conflict; and this is why it says harness the earth, and rule.
from Regeneration, Pages 156-158