ChU 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
Devanagari rendered by HREEM from the edition's roman (IAST) text; the IAST is the edition's own.
'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.'
Translated by F. Max Müller