Bhagavad Gita 16.24

16.24 Therefore, let the scripture be thy authority in determining what ought to be done and what ought not to be done. Having known what is said in the ordinance of the scriptures, thou shouldst act here in this world.

One should therefore understand what is duty and what is not duty by the regulations of the scriptures. Knowing such rules and regulations, one should act so that he may gradually be elevated.