Bhagavad Gita 2.28

अव्यक्तादिनि भूतानि व्यक्तिमध्यानि भारत |
अव्यक्तनिधानन्येव तत्र का परिदेवना

Translation

O scion of Bharat, all created beings are unmanifest before birth, manifest in life, and again unmanifest on death. So why grieve?