Katha-1-1-23-śatāyuṣaḥ

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

Though thus addressed, still Death said, to tempt him again. ‘Satâyushah, those who live a hundred years, i.e., centenarians; ask for centenarian sons and grandsons, besides, many cattle such as cows, etc., elephants, gold and horses. Ask for sovereignty over a large circuit of earth.’ And as all this would be useless, if he were himself short-lived, Death added ‘and yourself live as many years as you like with a body, where all the organs are vigorou.’

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