Taittiriya Upanishad 1.5.3

1.5.3

maha iti brahma /
brahmaṇā vāva sarve vedā mahīyante /
bhūriti vai prāṇaḥ /
bhuva ityapānaḥ /
suvariti vyānaḥ /
maha ityannam /
annena vāva sarve prāṇa mahīyante /
tā vā etāścatasraścaturdha /
catasraścatasro vyāhṛtayaḥ /
tā yo veda /
sa veda brahma /
sarve 'smai devā balimāvahanti // 3//
iti pañcamo 'nuvākaḥ //

Maha is Brahman (i.e. Om), for by Brahman (Om), indeed, are all the Vedas nourished. Bhūḥ, indeed, is prāṇa; Bhuvaḥ is apāna; Suvaḥ is vyāna; Maha is food; for by food, indeed, are all the vital forces nourished. These, then, that are four, are (each) fourfold. The Vyāhṛtis are divided into four groups of four (each). He who knows these knows Brahman. All the gods carry presents to him.