2:17 "Interwoven in his creation, the Spirit is beyond destruction. No one can bring to an end the Spirit which is everlasting."
The soul is eternal, we know that is a basic doctrine of Hinduism. This small verse also tells us why: souls are integrated into creation itself.
2:18 "For beyond time he dwells in these bodies, though these bodies have an end in their time; but he remains immeasurable, immortal. Therefore, great warrior, carry on thy fight."
The soul is not only immortal, but immeasurable. There were attempts in the last century to weigh the dying person at the moment of death the prove the existence of a soul by noting the difference between the weight of a dead versus living body. These experiments were debunked. Krishna tells us here that the soul is immeasurable. We must take its existence solely on faith.
2:19 "If any man thinks he slays, and if another thinks he is slain, neither knows the ways of the truth. The Eternal in man cannot kill: the Eternal in man cannot die."
Uh oh. Does this mean, then, that man has leave to kill indescriminantly? No - it only speaks of the condition of the soul, not the consequences of the act. But we're getting ahead of ourselves. There are two parts to this. The part of a man that is eternal - the soul, cannot kill because the soul cannot be killed. It is not the soul that is doing the harm but the current body. A body can kill a body.
2:20 "He is never born, and he never dies. He is in Eternity: he is for evermore. Never-born and eternal, beyond times gone or to come, he does not die when the body dies."
Here is an interesting notion. Is eternity timeless? Could this imply that reincarnation may not be (or does not have to be) linear? A soul could be reincarnated in a preceding era rather than solely in a succeeding era?
At the very least, it says that the soul does not age because it is never born; it simply is. It is beyond the measure of time
2:21 "When a man knows him as never-born, everlasting, never-changing, beyond all destruction, how can that man kill a man, or cause another to kill?"
Here is the answer to 2:19. If a man kills, it must be to higher purpose, otherwise, there is nothing gained by killing because man cannot die.
2:22 "As a man leaves on an old garment and puts on one that is new, the Spirit leaves his mortal body and then puts on one that is new."
Thinking about this concept is very freeing. It makes everyday life a lot less important. This life is not you. It is merely as a garment. Of what use is pride? What is important is only that which affects the Eternal self.