Bhagavad Gita

ಅಚ್ಛೇದ್ಯೋSಯಮದಾಹ್ಯೋSಯಮಕ್ಲೇದ್ಯೋSಶೋಷ್ಯ ಏವ ಚ ।
ನಿತ್ಯಃ ಸರ್ವಗತಸ್ಥಾಣುರಚಲೋSಯಂ ಸನಾತನಃ ॥೨೪॥
acchedyoSyamadāhyoSyamakledyoSśoṣya eva ca |
nityaḥ sarvagatasthāṇuracaloSyaṃ sanātanaḥ ||24||

Gist of the sloka:
Lord explains, that the individual soul cannot be destroyed by any of the 4 methods available, like earth, water, fire and air. The soul is the reflection of the universal Lord who himself above all the 4 types of gross elements. Being such a reflection, soul is subject to Vedic rules, regulations and limits.
Individual soul can never be destroyed by anyone at any time. This is the absolute truth. The soul basic qualities/swabhava can never be changed and he is reflection of the Lord.
Lord himself is the sole intent of the Vedas and is permanent in his qualities, each of which is infinite and complete in all aspects. There is no blemishes nor are his qualities limited. They are in fact, infinite.
Soul being a reflection of the Lord is also similarly unchanging and existent forever. Soul being protected by the Lord need not fear death and destruction.