Thereafter, Lord Viṣṇu entered the demons as the quality of passion, the demigods as the quality of goodness, and Vāsuki as the quality of ignorance to encourage them and increase their various types of strength and energy.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तथासुरानाविशदासुरेण रूपेण तेषां बलवीर्यमीरयन् । उद्दीपयन् देवगणांश्च विष्णु- र्दैवेन नागेन्द्रमबोधरूपः
tathāsurānāviśadāsureṇa rūpeṇa teṣāṃ balavīryamīrayan | uddīpayan devagaṇāṃśca viṣṇu- rdaivena nāgendramabodharūpaḥ
SB 8.7.11