BṚHADĀRAṆYAKA UPANISHAD · 1.3.3

अथ ह प्राणम् ऊचुस् त्वं न उद्गायेति ।
तथेति तेभ्यः प्राण उदगायत् ।
यः प्राणे भोगस् तं देवेभ्य आगायत् ।
यत् कल्याणं जिघ्रति तद् आत्मने ।
ते ऽविदुर् अनेन वै न उद्गात्रात्येष्यन्तीति ।
तम् अभिद्रुत्य पाप्मनाविध्यन् ।
स यः स पाप्मा यद् एवेदम् अप्रतिरूपं जिघ्रति ।
स एव स पाप्मा ॥

atha ha prāṇam ūcus tvaṃ na udgāyeti ।
tatheti tebhyaḥ prāṇa udagāyat ।
yaḥ prāṇe bhogas taṃ devebhya āgāyat ।
yat kalyāṇaṃ jighrati tad ātmane ।
te ’vidur anena vai na udgātrātyeṣyantīti ।
tam abhidrutya pāpmanāvidhyan ।
sa yaḥ sa pāpmā yad evedam apratirūpaṃ jighrati ।
sa eva sa pāpmā ॥

Then they (the Devas) said to breath (scent): 'Do thou sing out for us.' 'Yes,' said breath, and sang. Whatever delight there is in breath (smell), that he obtained for the Devas by singing; but that he smelled well, that was for himself. The Asuras knew: 'Verily, through this singer they will overcome us.' They therefore rushed at the singer, and pierced him with evil. That evil which consists in smelling what is bad, that is that evil.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)