BṚHADĀRAṆYAKA UPANISHAD · 4.3.3

अस्तमित आदित्ये याज्ञवल्क्य किंज्योतिर् एवायं पुरुष इति ।
चन्द्रमा एवास्य ज्योतिर् भवतीति ।
चन्द्रमसैवायं ज्योतिषास्ते पल्ययते कर्म कुरुते विपल्येतीति ।
एवम् एवैतद् याज्ञवल्क्य ॥

astamita āditye yājñavalkya kiṃjyotir evāyaṃ puruṣa iti ।
candramā evāsya jyotir bhavatīti ।
candramasaivāyaṃ jyotiṣāste palyayate karma kurute vipalyetīti ।
evam evaitad yājñavalkya ॥

Ganaka Vaideha said: 'When the sun has set, O Yâgñavalkya, what is then the light of man?' Yâgñavalkya replied: 'The moon indeed is his light; for, having the moon alone for his light, man sits, moves about, does his work, and returns.' Ganaka Vaideha said: 'So indeed it is, O Yâgñavalkya.'

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)