BṚHADĀRAṆYAKA UPANISHAD · 3.1.6

याज्ञवल्क्येति होवाच -- यद् इदम् अन्तरिक्षम् अनारम्बणम् इव केनाक्रमेण यजमानः स्वर्गं लोकम् आक्रमत इति ।
ब्रह्मणर्त्विजा मनसा चन्द्रेण ।
मनो वै यज्ञस्य ब्रह्मा ।
तद् यद् इदं मनः सो ऽसौ चन्द्रः स ब्रह्मा स मुक्तिः सातिमुक्तिर् इत्य् अतिमोक्षा ।
अथ संपदः ॥

yājñavalkyeti hovāca -- yad idam antarikṣam anārambaṇam iva kenākrameṇa yajamānaḥ svargaṃ lokam ākramata iti ।
brahmaṇartvijā manasā candreṇa ।
mano vai yajñasya brahmā ।
tad yad idaṃ manaḥ so ’sau candraḥ sa brahmā sa muktiḥ sātimuktir ity atimokṣā ।
atha saṃpadaḥ ॥

'Yâgñavalkya,' he said, 'this sky is, as it were, without an ascent (staircase.) By what approach does the sacrificer approach the Svarga world?' Yâgñavalkya said: 'By the Brahman priest, who is the mind (manas), who is the moon. For the mind is the Brahman of the sacrifice, and the mind is the moon, and he is the Brahman. This constitutes freedom, and perfect freedom. These are the complete deliverances (from death).' Next follow the achievements.

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