Kaṭha Upaniṣad 2.18

2.18

na jāyate mriyate vā vipaścin nāyaṃ kutaścin na babhūva kaścit /
ajo nityaḥ śāśvato 'yaṃ purāṇo na hanyate hanyamāne śarīre //

18. The wise one [i. e. the soul, the _ātman_, the self] is not born, nor dies. This one has not come from anywhere, has not become anyone. Unborn, constant, eternal, primeval, this one Is not slain when the body is slain. 19. If the slayer think to slay, If the slain think himself slain, Both these understand not. This one slays not, nor is slain.