Srimad-Bhagavatam: Canto 12 - Chapter 1 - Verse 24
Sanskrit:
नैष त्वया मनुष्येन्द्र वधमर्हति सर्पराट् ।अनेन पीतममृतमथ वा अजरामर: ॥ २४ ॥
ITRANS:
naiṣa tvayā manuṣyendravadham arhati sarpa-rāṭanena pītam amṛtamatha vā ajarāmaraḥ
Translation:
O King among men, it is not fitting that this king of snakes meet death at your hands, for he has drunk the nectar of the immortal demigods. Consequently he is not subject to the ordinary symptoms of old age and death.