Katha-2-3-14-yadā sarve

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

When of the person thus seeing the truth, all desires, which were clinging to the intellect of the knower before he attained the knowledge, fall off from want of anything else to be desired (for intellect and not the âtman is the seat of desires, and also from another sruti which says desire, volition, etc.), then the mortal (he was so before he attained the knowledge), subsequently to the acquisition of knowledge, becomes immortal, death consisting in ignorance, desire and karma being destroyed, and becomes Brahman even here (there being no necessity of going, death resulting in a going having been destroyed) like fire extinguished, all bondage being destroyed.

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