Mundaka-1-1-8-tapasā cīyate

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri

Com.—This mantra is begun for the purpose of stating the fixed order of creation. ‘By tapas,’ by knowledge of how to create the Brahman which is the source of all created things; ‘increases,’ i. e., becomes distended, being desirous to create the world as a seed when sending out the sprout, or as a father desirous of begetting a son dilates with joy; from the Brahman thus extended by its omniscience, i. e., by its knowledge and its power of creation, preservation and destruction of the universe; Annam means ‘that which is eaten or enjoyed’, i.e., the unmanifested (avyakritam) common to all in samsara is produced in the state fit for emancipation; and from “the unmanifested”, i. e., the “Annam” in the state fit for manifestation. Prana, i. e., Hiranyagarhha, the common cosmic entity, endowed with the power of knowledge and activity of the Brahman, the sprouting seed, as it were, of the totality of cosmic ignorance, desire, karma, and creatures and the Atman of the universe. “Is produced”, should be supplied. From that prana that which is called “mind” whose characteristic is volition, deliberation, doubt, determination, etc., is produced; and from that mind whose essence is volition, etc., what is called satyam, i.e., the five elements such as the akas, etc., are produced and from the five elements called satya, the seven worlds, the earth, etc., are produced in the order of the globes; and in them karma, for the living beings, man, etc., according to caste and the order of life, is produced; and with karma as the cause, its fruits. As long as karma is not destroyed, even by hundreds of millions of kalpa, so long is its fruit not destroyed. Hence it is called Amritam.

Links
Various resources on the Mundakopanishad
Upanishad Series – Mundakopanishad Commentary by Swami Chinmayananda