Maitri (Maitrāyaṇīya) Upaniṣad 6.4

6.4

athānyatrāpi uktamatha khalu ya udgīthaḥ sa praṇavo yaḥ praṇavaḥ sa udgītha iti asau vā āditya udgītha eṣa praṇavā iti | evaṃ hyāhodgīthaṃ praṇavākhyaṃ praṇetāraṃ bhārūpaṃ vigatanidraṃ vijaraṃ vimṛtyuṃ tripadaṃ tryakṣaraṃ punaḥ pañcadhā jñeyaṃ nihitaṃ guhāyāmityevaṃ hyāhordhvamūlaṃ tripādbrahma śākhā ākāśa vāyvagnyudakabhūmyādaya eko'śvatthanāmaitadbrahmaitasyaitattejo yadasā ādityaḥ omityetadakṣarasya caitattasmādomityanenaitadupāsītājasramityeko'sya sambodhayitetyevaṃ hyāha
etadevākṣaraṃ puṇyametadevākṣaraṃ param |
etadevākṣaraṃ jñātvā yo yadicchati tasya tat ||

4. Now it has elsewhere been said: ‘Now, then, the Udgītha is _Om_; _Om_ is the Udgītha. And so, verily, the Udgītha is yonder sun, and it is _Om_.’

For thus has it been said: ‘... the Udgītha, which is called _Om_, a leader, brilliant, sleepless, ageless, deathless, three-footed, three-syllabled, also to be known as fivefold, hidden in the secret place [of the heart].’

For thus has it been said: ‘The three-quartered Brahma

has its root above. Its branches are space, wind, fire, water, earth, and the like. This Brahma has the name of 'the Lone Fig-tree.' Belonging to It is the splendor which is yon sun, and the splendor too of the syllable *Om*. Therefore one should worship it with *Om* continually. He is the only enlightener of a man.'

For thus has it been said:—

That syllable, indeed, is holy (*puṇya*).
That syllable indeed is supreme.
By knowing that syllable, indeed,
Whatever one desires, is his!