Bhagavad Gita: Chapter 8, Verse 19

भूतग्राम: स एवायं भूत्वा भूत्वा प्रलीयते |
रात्र्यागमेऽवश: पार्थ प्रभवत्यहरागमे || 19||

bhūta-grāmaḥ sa evāyaṁ bhūtvā bhūtvā pralīyate
rātryāgame ’vaśhaḥ pārtha prabhavatyahar-āgame

bhūta-grāmaḥthe multitude of beings; saḥthese; evacertainly; ayamthis; bhūtvā bhūtvārepeatedly taking birth; pralīyatedissolves; rātri-āgamewith the advent of night; avaśhaḥhelpless; pārthaArjun, the son of Pritha; prabhavatibecome manifest; ahaḥ-āgamewith the advent of day

Translation

BG 8.19: The multitudes of beings repeatedly take birth with the advent of Brahma’s day, and are reabsorbed on the arrival of the cosmic night, to manifest again automatically on the advent of the next cosmic day.

Commentary

The Vedas list four pralayas (dissolutions):

Nitya Pralaya: This is the daily dissolution of our consciousness that takes place when we fall into deep sleep.

Naimittik Pralaya: This is the dissolution of all the abodes up to Mahar Lok at the end of Brahma’s day. At that time, the souls residing in these abodes become unmanifest. They reside in a state of suspended animation in the body of Vishnu. Again when the Brahma creates these lokas, they are given birth according to their past karmas.

Mahā Pralaya: This is the dissolution of the entire universe at the end of Brahma’s life. At this time, all the souls in the universe go into a state of suspended animation in the body of Maha Vishnu. Their gross (sthūl śharīr) and subtle (sūkṣhma śharīr) bodies dissolve, but the causal body (kāraṇ sharīr) remains. When the next cycle of creation takes place, they are again given birth, according to their sanskārs and karmas stored in their causal body.

Ātyantik Pralaya: When the soul finally attains God, it gets released from the cycle of birth and death forever. Ātyantik Pralaya is the dissolution of the bonds of Maya, which were tying the soul since eternity.