Bhagavad Gita Chapter 4.17
karmaṇo hy api boddhavyaḿ
boddhavyaḿ ca vikarmaṇaḥ
akarmaṇaś ca boddhavyaḿ
gahanā karmaṇo gatiḥ
Translation
The intricacies of action are very hard to understand. Therefore one should know properly what action is, what forbidden action is, and what inaction is.