CHĀNDOGYA UPANISHAD · 7.21.1

यदा वै करोत्य् अथ निस्तिष्ठति ।
नाकृत्वा निस्तिष्ठति ।
कृत्वैव निस्तिष्ठति ।
कृतिस् त्व् एव विजिज्ञासितव्येति ।
कृतिं भगवो विजिज्ञास इति ॥

yadā vai karoty atha nistiṣṭhati ।
nākṛtvā nistiṣṭhati ।
kṛtvaiva nistiṣṭhati ।
kṛtis tv eva vijijñāsitavyeti ।
kṛtiṃ bhagavo vijijñāsa iti ॥

'When one performs all sacred duties, then one attends really on a tutor. One who does not perform his duties, does not really attend on a tutor. Only he who performs his duties, attends on his tutor. This performance of duties, however, we must desire to understand.' 'Sir, I desire to understand it.'

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