Bhagavad Gita Chapter 8.18
avyaktād vyaktayaḥ sarvāḥ
prabhavanty ahar-āgame
rātry-āgame pralīyante
tatraivāvyakta-saḿjñake
Translation
At the beginning of Brahma’s day, all living entities become manifest from the unmanifest state, and thereafter, when the night falls, they are merged into the unmanifest again.