The Soul is not born, nor does It ever die. After having been present, It will not cease to be either. Unborn, ever present, permanent, most ancient, It is not killed when the body is killed.
This is the crux of the Sāṅkhya exposition. Through rational enquiry and introspection, it unearths the singular, all-fold presence, which endures always, does not become extinct at all. To grasp and realize it is the key to fulfilment of human life.
The war will last a few days. Except the few winning survivors, all warriors in both armies will die. Unless the spiritual truth of the Self, the ‘I’, is assimilated well, weakness, confusion and delusion will not leave.
Krishna repeats that the Self is unborn, undying, everpresent and eternal. Even when the body is slain, It will not be slain. So, be free of all grief.