Katha-2-2-14-tadetaditi

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

That bliss of the knowledge of the âtman which is indescribable, highest and which, though beyond the speech and mind of men, under the sway of Prakriti, they, the Brâhmins freed from all desire, describe as this, i.e., as something directly perceived; how; i.e., by what process shall I know that bliss: i.e., realise it as thus perceivable by my intelligence, as the sanyâsins freed from desire, do? Is that which is luminous of itself an object clearly perceivable by our intelligence or not?

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