CHĀNDOGYA UPANISHAD · 1.2.9

नैवैतेन सुरभि न दुर्गन्धि विजानाति ।
अपहतपाप्मा ह्य् एषः ।
तेन यद् अश्नाति यत् पिबति तेनेतरान् प्राणान् अवति ।
एतम् उ एवान्ततो ऽवित्त्वोत्क्रामति ।
व्याददात्य् एवान्तत इति ॥

naivaitena surabhi na durgandhi vijānāti ।
apahatapāpmā hy eṣaḥ ।
tena yad aśnāti yat pibati tenetarān prāṇān avati ।
etam u evāntato ’vittvotkrāmati ।
vyādadāty evāntata iti ॥

By it (the breath in the mouth) he distinguishes neither what is good nor what is bad-smelling, for that breath is free from evil. What we eat and drink with it supports the other vital breaths (i. e. the senses, such as smell, &c.) When at the time of death he does not find that breath (in the mouth, through which he eats and drinks and lives), then he departs. He opens the mouth at the time of death (as if wishing to eat).

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