Vishnupurana 6.4.9

6.4.9

padmayoner dinaṃ yat tu caturyugasahasravat
ekārṇave kṛte loke tāvatī rātrir iṣyate //

When the universal spirit wakes, the world revives; when he closes his eyes, all things fall upon the bed of mystic slumber. In like manner as a thousand great ages constitute a day of Brahmá, so his night consists of the same period; during which the world is submerged by a vast ocean. Awaking at the end of his night, the unborn, Vishńu, in the character of Brahmá, creates the universe anew, in the manner formerly related to you.