CHĀNDOGYA UPANISHAD · 1.2.2

ते ह नासिक्यं प्राणम् उद्गीथम् उपासां चक्रिरे ।
तं ह असुराः पाप्मना विविधुः ।
तस्मात् तेनोभयं जिघ्रति सुरभि च दुर्गन्धि च ।
पाप्मना ह्य् एष विद्धः ॥

te ha nāsikyaṃ prāṇam udgītham upāsāṃ cakrire ।
taṃ ha asurāḥ pāpmanā vividhuḥ ।
tasmāt tenobhayaṃ jighrati surabhi ca durgandhi ca ।
pāpmanā hy eṣa viddhaḥ ॥

They meditated on the udgîtha (Om) as the breath (scent) in the nose, but the Asuras pierced it (the breath) with evil. Therefore we smell by the breath in the nose both what is good-smelling and what is bad-smelling. For the breath was pierced by evil.

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