Katha-2-3-15-yadā sarve

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

When again, the up-rooting of all desires takes place is explained. When all the ties of the heart of one, while yet alive, i.e., all the modifications of the intellect due to ignorance which are in the nature of fast-bound knots are destroyed; when the ties of the heart, i.e., such as the beliefs ‘I am this body,’ ‘this is my wealth,’ ‘I am happy or miserable,’ etc., are destroyed by the rise of the contrary belief in the identity of the Brahman and the âtman, in the form ‘I am certainly Brahman not subject to Samsâra’ the desires which originate in those ties are destroyed to their very root; then the mortal becomes immortal. Thus much alone—the doubt that there is more should not be raised—is the instruction. Of all the Vedântâs’ should be supplied to complete the sentence,

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