CHĀNDOGYA UPANISHAD · 7.19.1

यदा वै श्रद्दधात्य् अथ मनुते ।
नाश्रद्दधन् मनुते ।
श्रद्दधद् एव मनुते ।
श्रद्धा त्व् एव विजिज्ञासितव्येति ।
श्रद्धां भगवो विजिज्ञास इति ॥

yadā vai śraddadhāty atha manute ।
nāśraddadhan manute ।
śraddadhad eva manute ।
śraddhā tv eva vijijñāsitavyeti ।
śraddhāṃ bhagavo vijijñāsa iti ॥

'When one believes, then one perceives. One who does not believe, does not perceive. Only he who believes, perceives. This belief, however, we must desire to understand.' 'Sir, I desire to understand it.'

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)