Krsna answers emphatically that such a one does not perish, either in the present or in the future. A good person will never meet with misfortune.
Krsna is stating the Law of Karma. As long as you are acting positively in the present your mind will be at peace and you are assured of success in future. So all you have to do is abide by your own conscience.
When you pursue the spiritual path you may or may not reach Enlightenment. However, you will be a happy and successful person. You will not be destroyed. The return depends on your present level and the effort you put in.
Punya is the fall. Punya is merit capital, the result of selfless, dedicated action. When you get involved in unselfish, spiritual activity you create unselfish desires which bind you to the world. You acquire merit, punya, which is so subtle and refined that you can only exhaust it in heaven. You live there for countless years. But you have to come back to the world because you have acquired desires.
You are then born in a prosperous and happy environment. You create the world you live in. Negative, selfish actions create a stressful, impoverished world. Unselfish, spiritual actions catapult you into a circumstance that is both prosperous as well as happy. Few people are truly happy but they are usually not prosperous. And those who are wealthy are mostly unhappy. The combination of affluence and happiness is possible only with spiritual living.
The causal body and subtle body express themselves through various gross bodies because one body is insufficient. Death is not a full stop but a comma from which you wake up and continue your march to Realisation.
This verse speaks of the Theory of Reincarnation. James Freeman Clarke says, “An idea that has occupied so many exceptional minds cannot be lightly dismissed. It is worthy of questioning, study and investigation.”