Bhagavad Gita 4.17
कर्मणो ह्यपि बोद्धव्यं बोद्धव्यं च विकर्मणः। अकर्मणश्च बोद्धव्यं गहना कर्मणो गतिः।।4.17।।
karmaṇo hyapi boddhavyaṃ boddhavyaṃ ca vikarmaṇaḥ| akarmaṇaśca boddhavyaṃ gahanā karmaṇo gatiḥ||4.17||
karmano hyapi boddhavyam boddhavyam ca vikarmanah akarmanashca boddhavyam gahana karmano gatih4.17
Meaning
One must understand the nature of prescribed action, forbidden action, and inaction. The truth about action is deep and difficult to comprehend.
कर्म का (स्वरूप) जानना चाहिये और विकर्म का (स्वरूप) भी जानना चाहिये; (बोद्धव्यम्) तथा अकर्म का भी (स्वरूप) जानना चाहिये (क्योंकि) कर्म की गति गहन है।
This is verse 17 of 42 in Chapter 4 (Jnana Karma Sanyasa Yoga) of the Bhagavad Gita.