Katha-1-1-6-anupaśya

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

Remember and reflect how your deceased ancestor’s father, grandfather and the rest conducted themselves; seeing them, it behoves you to travel in their path; see also how others, good men, now behave. There never was or is any falsehood in them; falsifying one’s word is the manner of bad men and none who has broken his word can ever become undecaying and immortal. What is there gained by breaking one’s word, seeing that man decays and dies like corn and is again born like corn in this, transitory world of the Jîvas? The meaning is ‘protect your truth and send me to Death.’

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