Bhagavad Gita 2.28

अव्यक्तादीनि भूतानि व्यक्तमध्यानि भारत ।
अव्यक्तनिधनान्येव तत्र का परिदेवना  ॥

avyaktādīni bhūtāni vyakta-madhyāni bhārata
avyakta-nidhanāny-eva tatra kā paridevanā – 2.28

The beginning of all beings is indistinct. Their end too is unknown. The middle state, namely the duration called life, is alone distinct. This being so, what is the point in grieving?