The Bhagavad Gita with Commentaries of Ramanuja, Madhva, Shankara and Others.
Bhagavad Gita 8.18
http://www.bhagavad-gita.us/articles/348/1/Bhagavad-Gita-818/Page1.html
By Bhagavan Sri Krishna
 

Text 18

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

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.

Commentary by Srila Prabhupada

No commentary by Srila Prabhupada.

Commentary by Sri Visvanatha Cakravarti Thakur

Those who are inferior,  residing within the three planetary systems, perish day after day. Madhusudana Sarasvati says: the word avyakta refers to Brahma in his sleeping state (not a total dissolution), since during the daily creation and dissolution of the universe, the elements remain intake. Then from a sleeping state (avyaktat), through Brahma, the places of enjoyment in the form of bodies and objects of enjoyment manifest (vyaktaya), or become suitable for use. At the coming of night, when Brahma sleeps, everything disappears within him.