BG 4.17
कर्मणो ह्यपि बोद्धव्यं बोद्धव्यं च विकर्मणः ।
अकर्मणश्च बोद्धव्यं गहना कर्मणो गतिः ॥
अकर्मणश्च बोद्धव्यं गहना कर्मणो गतिः ॥
karmaṇo hy api boddhavyaṁ boddhavyaṁ ca vikarmaṇaḥ
akarmaṇaś ca boddhavyaṁ gahanā karmaṇo gatiḥ
akarmaṇaś ca boddhavyaṁ gahanā karmaṇo gatiḥ
Word-for-word meanings
karmaṇaḥ api — [the truth] of prescribed action; boddhavyam — should be understood; ca — and; vikarmaṇaḥ — [the truth] of prohibited action; boddhavyam — should be understood; ca — and; akarmaṇaḥ — [the truth] of inaction; boddhavyam — should be understood; hi — because; gatiḥ — the internal mechanics; karmaṇaḥ — of action; gahanā — are difficult to grasp.
Translation
One should understand the truth about prescribed action, prohibited action, and inaction, since the internal mechanics of action are difficult to grasp.