Be'er Mayim Chaim, Genesis 11:30/באר מים חיים·בראשית י״א:ל׳

2And there are accordingly two types of procreation: One is in the world's physical dimension, which is sons and daughters, to increase their offspring like the dust of the land, since it was created to be inhabited (alluding to Isaiah 45:18). And the second is the procreation of souls in the higher world through [fulfillment of] the commandments and good deeds. For it is from there that the souls of converts and penitents come, as is known from the words of our teacher, Ari, may his memory be blessed. The essence of this is when a man and a woman cohabit with a true intention for the sake of God with fear and love, with the desired intentions before the One who spoke and the world came into being. And when she does not become pregnant from this cohabitation, those souls are created. In this way, Abraham would convert the men and Sarah the women, like the statement of the Sages, may their memory be blessed (Bereishit Rabbah 39:4). As they gave birth to these souls. And it is about them that it is stated: and the souls that they had made (Genesis 12:5) — that they actually made, for the souls [came] from them. And about this, the woman is the same as the man. For she, too, must seek to bring about new souls and spirits through her good actions. As the main descendants of the righteous are [their] good deeds. Hence the intention of that which was stated, Be fruitful and multiply (Genesis 1:28), was about this reproduction. Concerning this, the two of them are the same; in creating "fruit" above to increase the souls in the higher world. However, the command about procreation in the world is like its straightforward understanding, to produce children for the survival of the species. That is what is stated afterward: and fill the earth and subdue it. (For otherwise, one of [these phrases] would be superfluous. And understand [this]). As this is to fill the lower world, to increase the likeness and image of God in the world. And it is concerning this that it is stated, and conquer it — it is the manner of a man to conquer, and it is not the manner of a woman (Yevamot 65b). And that is why he is commanded and not she. And see there, as we have explained it. And that is why Scripture here states about that which she was barren, that you not say that she was completely barren, such that she did not give birth to anything in the world, that it is not like that: It is rather that she had no child. As she did not have a child with a body and soul in this world. But she continuously gave birth to souls by themselves, and made the souls for the converts, as mentioned. (After I wrote [this], I found it explicitly so in the holy Zohar, Parashat Shelach 168, see there.)