Chandogya Upanishad 4.12

atha ha enam anvāhāryapacano 'nuśaśāsa āpo diśo nakṣatrāṇi candramā iti ya eṣa candramasi puruṣo dṛśyate so 'ham asmi sa eva aham asmi iti

Then the Anvâhârya fire taught him: 'Water, the quarters, the stars, the moon (these are my forms). The person that is seen in the moon, I am he, I am he indeed.

sa ya etam evaṃ vidvān upāste apahate pāpakṛtyām lokī bhavati sarvam āyur eti jyog jīvati na asya avarapuruṣāḥ kṣīyante upa vayaṃ taṃ bhuñjāmo 'smiṃś ca loke 'muṣmiṃś ca ya etam evaṃ vidvān upāste

He who knowing this meditates on him, destroys sin, obtains the world (of Agni Anvâhârya), reaches his full age, and lives long; his descendants do not perish. We guard him in this world and in the other, whosoever knowing this meditates on him.'