KAṬHA UPANISHAD · 2.2.14

तदेतदिति मन्यन्तेऽनिर्देश्यं परमं सुखम् ।
कथं नु तद्विजानीयां किमु भाति विभाति वा ॥ १४॥

tadetaditi manyante’nirdeśyaṃ paramaṃ sukham ।
kathaṃ nu tadvijānīyāṃ kimu bhāti vibhāti vā ॥ 14॥

“This is He,” is all they can realise of Him, a highest felicity which none can point to nor any define it. How shall I know of Him whether He shineth or reflecteth one light and another?