Taittiriya Upanishad 3.1

3.1.1

āūṃ saha nāvavatu /
saha nau bhunaktu /
saha vīryaṃ karavāvahai /
tejasvi nāvadhītamastu mā vidviṣāvahai /
āūṃ śāntiḥ śāntiḥ śāntiḥ //
bhṛgurvai vāruṇiḥ /
varuṇaṃ pitaramupasasāra /
adhīhi bhagavo brahmeti /
tasmā etatprovāca /
annaṃ prāṇaṃ cakṣuḥ śrotraṃ mano vācamiti /
tam̐ hovāca /
yato vā imāni bhūtāni jāyante /
yena jātāni jīvanti /
yatprayanyabhisam̐viśanti /
tadvijijñāsasva /
tadbrahmeti /
sa tapo 'tapyata /
sa tapastaptvā // 1//
iti prathamo 'nuvākaḥ //

1. Bhṛigu Vāruṇi, verily, approached his father Varuṇa, and said: ‘Declare Brahma, Sir!’

To him he taught that as food, as breath, as sight, as hearing, as mind, as speech.

Then he said to him: ‘That, verily, whence beings here are born, that by which when born they live, that into which on deceasing they enter—that be desirous of understanding. That is Brahma.’

He performed austerity. Having performed austerity, he understood that Brahma is food. For truly, indeed, beings here are born from food, when born they live by food, on deceasing they enter into food.