Katha-2-1-9-yataścodeti

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

Moreover, that prâna from which the sun rises and that where alone the sun every day sets, that prana. i.e., the Adhidaiva and the Adhyâtma aspect of Atman as the gods and speech, etc., as the senses enter into, while they last, as spokes in a wheel. Even he is certainly Brahman. That is this Brahman, the âtman of all. None certainly passes beyond that] none ceasing to be of the nature of that becomes other than that. This verily is that.

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