त्रिलोक्या युगसाहस्रं बहिराब्रह्मणो दिनम् तावत्येव निशा तात यन्निमीलति विश्वसृक्
trilokyā yuga-sāhasraṁ bahir ābrahmaṇo dinam tāvaty eva niśā tāta yan nimīlati viśvasṛk
Synonyms
trilokyāḥ—of the three worlds; yuga—the four yugas; sāhasram—one thousand; bahiḥ—outside of; ābrahmaṇaḥ—up to Brahmaloka; dinam—is a day; tāvatī—a similar (period); eva—certainly; niśā—is night; tāta—O dear one; yat—because; nimīlati—goes to sleep; viśvasṛk—Brahmā..
Translation
Outside of the three planetary systems [Svarga, Martya and Pātāla], the four yugas multiplied by 1,000 comprise one day on the planet of Brahmā. A similar period comprises a night of Brahmā, in which the creator of the universe goes to sleep.
Purport
When Brahmā goes to sleep in his nighttime, the three planetary systems below Brahmaloka are all submerged in the water of devastation. In his sleeping condition, Brahmā dreams about the Garbhodakaśāyī Viṣṇu and takes instruction from the Lord for the rehabilitation of the devastated area of space.