The Mundaka Upanishad, Chapter 2, Section 1, Verse 5, as translated by Sri Aurobindo: “From Him is fire, of which the Sun is the fuel, then rain from the Soma, herbs upon the earth, and the male casts his seed into woman: thus are these many peoples born from the Spirit.”
The divine Spirit is not simply an Absolute, separated from the universal creation; rather, the Spirit manifests the creation out of his own substance. The essential nature of the Divine, Sat-Chit-Ananda, Existence-Consciousness-Bliss develops a transitional process by which universal powers are put forth, and these powers then act to create the individualised forms and details which we recognize as Matter, Life and Mind. The transitional activity is undertaken by a mediating power of consciousness, which Sri Aurobindo calls the “supramental” consciousness, which maintains its full awareness of the source in the divine unity of Sat-Chit-Ananda, while concurrently differentiating forms to create the multiplicity.
In this verse, the reference to fire is Agni, the “knower of all things born” and the power over Matter. It’s source is the Sun, which in an inner sense represents the massed light of the supramental consciousness, and which externally is obviously the provider of life-giving heat and light energy. Rain from Soma represents another inner experience that can occur as the consciousness opens (and which has been described in various texts on Yoga), and externally, there is a link between the moon and the behavior of water. Soma in the ancient texts refers not only to a mystical bliss-giving drink, but to Chandra, the moon. Thus, both an esoteric and an outer sense is conveyed through the symbols.
Out of the earth come the plant-life, or herbs as translated here, and they provide sustenance to animal life. In the animal and human forms, the process of procreation involves the joining of the seed of the man with the ovum in the woman, thus creating a process for evolutionary development of forms and the creation of ongoing generations of life, all being consequences of the original conscious Existent undertaking a process of creation and manifestation in what we know as the universe.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210