Chandogya Upanishad 6.8.3

6.8.3

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 \\608.3\

3. Understand from me, my dear, hunger (aśanā) and thirst. When a person here is hungry (aśiśiṣati), as it is called, just water is leading off (nayati) that which has been eaten (√aś). So, as they speak of "a leader-of-cows" (go-nāya), "a leader-of-horses" (aśva-nāya), "a leader-of-men" (puruṣa-nāya), so they speak of water as "a leader-of-food" (aśa-nāya, hunger).

On this point, my dear, understand that this [body] is a sprout which has sprung up. It will not be without a root.