Shiva Purana

siva.sh/siva-purana/uma-samhita/15/11

तस्याधारः स्थितो नागस्स च विष्णुः प्रकीर्तितः ।। ब्रह्मणो वचसो हेतोर्बिभर्ति सकलं त्विदम् ।। ११ ।।

sanskrit

Its support is the serpent Śeṣa. He is glorified as Viṣṇu. At the instance of Brahmā he supports all this.

english translation

tasyAdhAraH sthito nAgassa ca viSNuH prakIrtitaH || brahmaNo vacaso hetorbibharti sakalaM tvidam || 11 ||

hk transliteration by Sanscript