Brihadaranyaka Upanishad 3.1.6

3.1.6

yājñavalkyeti hovāca yadidamantarikṣamanārambaṇamiva kenākrameṇa yajamānaḥ svargaṃ lokamākramata iti brahmaṇartvijā manasā candreṇa mano vai yajñasya brahmā tadyadidaṃ manaḥ so'sau candraḥ sabrahmā sa muktiḥ sātimuktirityatimokṣā atha saṃpadaḥ

'Yâjnavalkya,' said he, 'since the sky is, as it were, without a support, through what support does the sacrificer go to heaven?' 'Through the mind—through the moon, which is the (real) priest called Brahmâ.footnote{Who supervises the functions.} The mind of the sacrificer is the Brahmâ. This mind is the moon; the moon is the Brahmâ; this (moon) is liberation; this (liberation) is emancipation.' So far about the ways of emancipation; now about the meditation based on resemblance.