Katha-1-2-22-aśarīram̐

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

This text shows that by knowing him, grief also vanishes. ‘Bodiless,’ the âtman being like the âkâs by its own nature; ‘bodies,’ bodies of the gods, the manes, men and the rest. ‘Perishable,’ devoid of firmness, not eternal; ‘firmly seate,’ eternal, i.e., not subject to modifications; ‘great,’ to avoid the doubt that the greatness may be relative, the text adds ‘all-pervading.’ The word ‘âtman’ is used to show that it is not distinct from one’s Self. The word âtman is primarily used to denote the Pratyagâtman, i.e., the âtman in the body. Having known the âtman of this description, i.e., having realised him in the form ‘I am he,’ the intelligent do not grieve. There is no occasion for such a knower of the âtman to grieve.

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