Like a great mountain, the Lord stands as the abode for all moving and nonmoving living entities. He is the friend of the snakes because Lord Ananta is His friend. As a mountain has thousands of golden peaks, so the Lord was seen with the thousands of golden-helmeted hoods of Ananta-nāga; and as a mountain is sometimes filled with jewels, so also His transcendental body was fully decorated with valuable jewels. As a mountains is sometimes submerged in the ocean water, so the Lord is sometimes submerged in the water of devastation.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
चराचरौको भगवन् महीध्र- महीन्द्रबन्धुं सलिलोपगूढम् । किरीटसाहस्रहिरण्यशृङ्ग- माविर्भवत्कौस्तुभरत्नगर्भम्
carācarauko bhagavan mahīdhra- mahīndrabandhuṃ salilopagūḍham | kirīṭasāhasrahiraṇyaśṛṅga- māvirbhavatkaustubharatnagarbham
SB 3.8.30