Bhagwad Gita
Chapter 2, Verse 30
देही नित्यमवध्योऽयं देहे सर्वस्य भारत।
तस्मात्सर्वाणि भूतानि न त्वं शोचितुमर्हसि।।2.30।।
O descendant of Bharat, he who dwells in the body is eternal and can never be slain. Therefore you need not grieve for any creature.