Bhagavatapurana 6.17.39

6.17.39

etat te sarvamākhyātaṃ yan māṃ tvaṃ paripṛcchasi /
vṛtrasyāsurajāteśca kāraṇaṃ bhagavanmateḥ //

39. I have thus told thee everything about which enquiry was made by thee, to wit, the cause of (what led to) Vritra’s birth in the Asura race and how his knowledge and devotion to Hari (were not lost).