Bhagavad Gita: Brahma's day (Attaining the Supreme,Text 18, Chapter 8)

Sri-bhagavan uvaca

avyaktad vyaktayah sarvah
prabhavanty ahar-agame
ratry-agame praliyante
tatraivavyakta-samjnake

          

   (Attaining the Supreme ,Text 18, Chapter 8)

Meaning: 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.

Bhagavad Gita: Brahma's day (Attaining the Supreme,Text 18, Chapter 8)