Kaṭha Upaniṣad 53

53

devair atrāpi vicikitsitaṃ kila tvaṃ ca mṛtyo yan na sujñeyam āttha /
vaktā cāsya tvādṛg anyo na labhyo nānyo varas tulya etasya kaścit ///1,1.22 //

Shankara’s Commentary:
Com.—Thus addressed, Nachiketas said, ‘I have heard from yourself that even the gods had doubt on this point and you say, Oh Death, that the true nature of the atman is not easy to know. As this cannot be known even by the learned, another, learned like you 2 to explain this, cannot be found, though sought.’ This boon also is a means to the attainment of emancipation and there is no other boon which can at all weigh with this. The meaning is that other boons bear only transitory fruits.