Brahman, the eternal soul, was never born and will never die, nor does it grow or decay. That spiritual soul is actually the knower of the youth, middle age and death of the material body. Thus the soul can be understood to be pure consciousness, existing everywhere at all times and never being destroyed. Just as the life air within the body, although one, becomes manifest as many in contact with the various material senses, the one soul appears to assume various material designations in contact with the material body.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
नात्मा जजान न मरिष्यति नैधतेऽसौ न क्षीयते सवनविद्व्यभिचारिणां हि । सर्वत्र शश्वदनपाय्युपलब्धिमात्रं प्राणो यथेन्द्रियबलेन विकल्पितं सत्
nātmā jajāna na mariṣyati naidhate'sau na kṣīyate savanavidvyabhicāriṇāṃ hi | sarvatra śaśvadanapāyyupalabdhimātraṃ prāṇo yathendriyabalena vikalpitaṃ sat
SB 11.3.38