CHĀNDOGYA UPANISHAD · 6.8.3

अशनापिपासे मे सोम्य विजानीहीति ।
यत्रैतत् पुरुषो ऽशिशिषति नामाप एव तद् अशितं नयन्ते ।
तद् यथा गोनायो ऽश्वनायः पुरुषनाय इत्य् एवं तद् अप आचक्षते ऽशनायेति ।
तत्रैतच् छुङ्गम् उत्पतितं सोम्य विजानीहि ।
नेदम् अमूलं भविष्यतीति ॥

aśanāpipāse me somya vijānīhīti ।
yatraitat puruṣo ’śiśiṣati nāmāpa eva tad aśitaṃ nayante ।
tad yathā gonāyo ’śvanāyaḥ puruṣanāya ity evaṃ tad apa ācakṣate ’śanāyeti ।
tatraitac chuṅgam utpatitaṃ somya vijānīhi ।
nedam amūlaṃ bhaviṣyatīti ॥

'Learn from me, my son, what are hunger and thirst. When a man is thus said to be hungry, water is carrying away (digests) what has been eaten by him. Therefore as they speak of a cow-leader (go-nâya), a horse-leader (asva-nâya), a man-leader (purusha-nâya), so they call water (which digests food and causes hunger) food-leader (asa-nâya). Thus (by food digested &c.), my son, know this offshoot (the body) to be brought forth, for this (body) could not be without a root (cause).

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)