When Brahma's day is manifest, this multitude of living entities comes into being, and at the arrival of Brahma's night they are all annihilated. BG 8.18 - 1972

Expressions researched:
"When Brahmā's day is manifest, this multitude of living entities comes into being, and at the arrival of Brahmā's night they are all annihilated"

Bhagavad-gita As it is

BG Chapters 7 - 12

When Brahmā's day is manifest, this multitude of living entities comes into being, and at the arrival of Brahmā's night they are all annihilated.

BG 8.18 (1972), Translation and Purport

When Brahmā's day is manifest, this multitude of living entities comes into being, and at the arrival of Brahmā's night they are all annihilated.

The less intelligent jīvas try to remain within this material world and are accordingly elevated and degraded in the various planetary systems. During the daytime of Brahmā they exhibit their activities, and at the coming of Brahmā's night they are annihilated. In the day they receive various bodies for material activities, and at night these bodies perish. The jīvas (individual souls) remain compact in the body of Viṣṇu and again and again are manifest at the arrival of Brahmā's day. When Brahmā's life is finally finished, they are all annihilated and remain unmanifest for millions and millions of years. Finally, when Brahmā is born again in another millennium, they are again manifest. In this way the jīvas are captivated by the material world. However, those intelligent beings who take to Kṛṣṇa consciousness and chant Hare Kṛṣṇa, Hare Rāma in devotional service transfer themselves, even in this life, to the spiritual planet of Kṛṣṇa and become eternally blissful there, not being subject to such rebirths.