There is this doubt about a man who has departed — some say he is, others that he is not. Taught by you I would know this. Of the boons, this is the third I choose.
Katha Upanishad
कठोपनिषद्
मूल श्लोकः
येयं प्रेते विचिकित्सा मनुष्येऽस्तीत्येके नायमस्तीति चैके। एतद्विद्यामनुशिष्टस्त्वयाहं वराणामेष वरस्तृतीयः॥
yeyaṁ prete vicikitsā manuṣye 'stīty eke nāyam astīti caike etad vidyām anuśiṣṭas tvayāhaṁ varāṇām eṣa varas tṛtīyaḥ
KaU 1.20