Katha-2-2-2-ham̐saḥ

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

And he the âtman does not live in the city of one body alone; but he lives in all cities. How hamsah ] one who moves; suchishat ] dwelling in heaven as the sun. Vasuh, one who animates all; dwells in the inter-space, as wind; hôtâ ] fire, according to the sruti ‘fire indeed is hôtâ;’ Vêdishat ] dwelling in Vêdi or earth, according to the srutis ‘ this Vêdi is the supreme nature of earth,’ etc. Atithih ] sômah. Durônasat ] dwelling in Durôna, i.e., vessel; or a Brâhmin dwelling in the house (Durôna) as a guest (atithih); nrishat ] dwelling in men; Varasat ] dwelling in betters, i.e., the Devas. Ritasat dwelling in rita, i.e., truth or sacrifice; Vyômasat dwelling in Vyôma, i.e., âkâsa, Abjâh ] those born in water, in the form of conch, mother of pearl, whale, etc.; gojâh ] those born of the earth in the form of corn, grain, etc.; ritajâh, those born in the form of appendages ta sacrifice; adrijâh ] those born of mountains in the form of rivers, etc.; though the âtman of all, he is ritam, i.e., of unchanging nature. Brihat, great, being the cause of all; even when the sun alone is described by the mantra, even then, from the fact that the sun is accepted as âtman in his nature, there is no conflict in this commentary. The meaning of the mantra is that the âtman of the universe is only one and all-pervading and there is no difference in the âtman.

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