Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 13
Sanskrit:
अधोऽसुराणां नागानां भूमेरोकोऽसृजत् प्रभुः ।त्रिलोक्यां गतयः सर्वाः कर्मणां त्रिगुणात्मनाम् ॥ १३ ॥
ITRANS:
adho ’surāṇāṁ nāgānāṁbhūmer oko ’sṛjat prabhuḥtri-lokyāṁ gatayaḥ sarvāḥkarmaṇāṁ tri-guṇātmanām
Translation:
Lord Brahmā created the region below the earth for the demons and the Nāga snakes. In this way the destinations of the three worlds were arranged as the corresponding reactions for different kinds of work performed within the three modes of nature.