Chapter 8, Verse 18
Part of 8: Akṣhar Brahma Yog — अक्षरब्रह्मयोगअव्यक्ताद्व्यक्तयः सर्वाः प्रभवन्त्यहरागमे। रात्र्यागमे प्रलीयन्ते तत्रैवाव्यक्तसंज्ञके॥
avyaktād vyaktayaḥ sarvāḥ prabhavantyahar-āgame rātryāgame pralīyante tatraivāvyakta-sanjñake
From the Unmanifested, all the manifested worlds proceed upon the arrival of the 'day'; upon the arrival of the 'night', they dissolve indeed into that which is known as the Unmanifested.
When Brahma awakes, all manifestations, moving and unmoving (animate and inanimate) stream forth at the coming of the day from the Avyakta or the Unmanifested. When Brahma goes to sleep, all the manifestations merge in the Unmanifested, for the cosmic night has set in. Coming of the day Commencement of creation. Coming of the night Commencement of dissolution. (Cf. IX.7and8)