Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 12
Sanskrit:
यत्र हि महाहिप्रवरशिरोमणय: सर्वं तम: प्रबाधन्ते ॥ १२ ॥
ITRANS:
yatra hi mahāhi-pravara-śiro-maṇayaḥ sarvaṁ tamaḥ prabādhante.
Translation:
Many great serpents reside there with gems on their hoods, and the effulgence of these gems dissipates the darkness in all directions.