KAṬHA UPANISHAD · 1.1.22

देवैरत्रापि विचिकित्सितं किल
त्वं च मृत्यो यन्न सुज्ञेयमात्थ ।
वक्ता चास्य त्वादृगन्यो न लभ्यो
नान्यो वरस्तुल्य एतस्य कश्चित् ॥ २२॥

devairatrāpi vicikitsitaṃ kila
tvaṃ ca mṛtyo yanna sujñeyamāttha ।
vaktā cāsya tvādṛganyo na labhyo
nānyo varastulya etasya kaścit ॥ 22॥

“Even by the gods was this debated, it is sure, and thou thyself hast said that it is not easy of knowledge; never shall I find another like thee to tell of it, nor is there any other boon that is its equal.”