Katha-2-1-10-yadeveha

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

This is said in order that the doubt may not arise in anybody; that what exists in all from the Brahma down to the immovable and appears, being subject to particular conditions, as something other than Brahman and subject to samsâra, he is different from the highest Brahman. What indeed is here subject to conditions of causes and effects and appears to the ignorant as possessing the attributes of sâmsâra, he is indeed the Brahman there centred within the body, in his nature dense with eternal knowledge and devoid of the attributes of all samsâra; again, what there is centred with self is itself here subject to conditions of name, form, cause and effect and is no other. This being so, he who here deluded by ignorance, which consists in seeing difference by the nature of the conditions sees in the Brahman which is one, a variety, thinking thus ‘I am other than the highest Brahman and the highest Brahman is other than I’, goes from death to death, i.e., is again born and dies; so, one should not see thus. The drift of the text is that one should see thus. ‘I am indeed the Brahman, the one unalloyed intelligence, all-pervading, filling all space like the âkâs’.

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