Bhagavad Gita

ದೇಹೀ ನಿತ್ಯಮವಧ್ಯೋSಯಂ ದೇಹೇ ಸರ್ವಸ್ಯ ಭಾರತ ।
ತಸ್ಮಾತ್ ಸರ್ವಾಣಿ ಭೂತಾನಿ ನ ತ್ವಂ ಶೋಚಿತುಮರ್ಹಸಿ ॥೩೦॥
dehī nityamavadhyoSyaṃ dehe sarvasya bhārata |
tasmāt sarvāṇi bhūtāni na tvaṃ śocitumarhasi ||30||

Gist of the sloka:
O Bharatha, in all beings the soul cannot be killed [Lord himself guards the soul] therefore lamenting for its death is not appropriate.
The truth is, the soul residing in the body cannot be killed, but the body can be. One should therefore should not undergo grief for it. One cannot exit from the body on own will either. Nor can one, enter a body on its own will. Nor can one remain in the body forever. The actions are controlled by the Lord.
When the Lord is resident with the soul in the body it’s not appropriate to think otherwise about birth and death. Once a person understands this, birth or death becomes immaterial and death becomes a pleasurable event.
Few strange thoughts might appear in some. As there is no death, is it ok to go ahead and kill someone?
This thought process is not correct. The knowledge which we have gained so far is related to us on an individual level. We are living in a society and we are bound to follow the societal dharma [kula dharma] and not act against the very society.
Neither does the knowledge give us the right to utilize it for individual mischief, justifying it under the true knowledge. The knowledge so given is to elevate the soul towards the Lord. Actions misusing the knowledge would only lead us away from the Lord.