Bhagavad Gita Chapter 2, Verse 12

न त्वेवाहं जातु नासं न त्वं नेमे जनाधिपाः | न चैव न भविष्यामः सर्वे वयमतः परम् ||

na tv evāhaṁ jātu nāsaṁ na tvaṁ neme janādhipāḥ na caiva na bhaviṣyāmaḥ sarve vayam ataḥ param

Never was there a time when I did not exist, nor you, nor these kings. Nor will there ever be a time hereafter when we shall cease to exist.

Krishna's opening declaration cuts to the core: we are eternal. There was never a time when you, I, or these warriors didn't exist—and never will be. He's not talking about bodies being reborn; he's pointing to the ātman (eternal self) that never begins or ends. Notice the phrasing: 'did not exist' (not 'was not born'), 'cease to exist' (not 'die'). This distinction matters—existence itself is eternal. If the soul can't die, Arjuna's grief about killing is based on confusion. You can't destroy what's immortal.