Lord Krishna describes material body to be perishable either now or after a 100 years, it’s just a matter of timeĀ but the soul is indestructible.
He said that the dimensions of the spirit soul are so tiny that nobody can even see it therefore there is no question of it being ever destroyed.
It is the soul which maintains the material body and as soon as it leaves the material body, the body begins to decompose.
Therefore we should never lamentĀ over the death of any person as his soul can never be destroyed and he is destined to get a new body according to his past deeds.