Chapter 4 · Knowledge and Renunciation of Action · Krishna said
Bhagavad Gita 4.17 — The deep way of action
कर्मणो ह्यपि बोद्धव्यं बोद्धव्यं च विकर्मणः। अकर्मणश्च बोद्धव्यं गहना कर्मणो गतिः ॥
karmaṇo hyapi boddhavyaṃ boddhavyaṃ ca vikarmaṇaḥ | akarmaṇaśca boddhavyaṃ gahanā karmaṇo gatiḥ ||
Meaning
One must understand what action is, what wrong action is, and what inaction is. The way of action is very deep.