Into that universal lotus flower Lord Viṣṇu personally entered as the Supersoul, and when it was thus impregnated with all the modes of material nature, the personality of Vedic wisdom, whom we call the self-born, was generated.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तल्लोकपद्मं स उ एव विष्णुः प्रावीविशत्सर्वगुणावभासम् । तस्मिन् स्वयं वेदमयो विधाता स्वयम्भुवं यं स्म वदन्ति सोऽभूत्
tallokapadmaṃ sa u eva viṣṇuḥ prāvīviśatsarvaguṇāvabhāsam | tasmin svayaṃ vedamayo vidhātā svayambhuvaṃ yaṃ sma vadanti so'bhūt
SB 3.8.15