Bhagavad Gita · 2.26

अथ चैनं नित्यजातं नित्यं वा मन्यसे मृतम्।तथापि त्वं महाबाहो नैवं शोचितुमर्हसि॥

atha chainaṁ nitya-jātaṁ nityaṁ vā manyase mṛtam tathāpi tvaṁ mahā-bāho naivaṁ śhochitum arhasi

Even if you think the soul is perpetually born and perpetually dies, still, O mighty-armed one, you should not grieve.

— Bhagavad Gita 2.26

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)