Chāndogya Upaniṣad 1.2.9

1.2.9

naivaitena surabhi na durgandhi vijānāti \
apahatapāpmā hy eṣaḥ \
tena yad aśnāti yat pibati tenetarān prāṇān avati \
etam u evāntato (S ) \
vyādadāti evāntata iti \\102.9\

9. With this [breath] one discerns neither the sweet-smelling nor the ill-smelling, for it is free from evil. Whatever one eats with this, whatever one drinks with this, he protects the other vital breaths. And, not finding this [breath in the mouth], one finally deceases; one finally leaves his mouth open.