Chapter 4 · verse 17 · gita.yoga.org

Bhagavad Gita 4.17

कर्मणो ह्यपि बोद्धव्यं बोद्धव्यं च विकर्मणः। अकर्मणश्च बोद्धव्यं गहना कर्मणो गतिः

For verily, the true nature of action enjoined by the scriptures should be known, as well as that of forbidden or unlawful action, and of inaction; the nature of action is hard to understand.