Bhagavad Gita Chapter 18, Verse 45
स्वे स्वे कर्मण्यभिरतः संसिद्धिं लभते नरः | स्वकर्मनिरतः सिद्धिं यथा विन्दति तच्छृणु ||
sve sve karmaṇy abhirataḥ saṁsiddhiṁ labhate naraḥ svakarma-nirataḥ siddhiṁ yathā vindati tac chṛṇu
A person attains perfection by being devoted to one's own duty. Hear how one devoted to one's own duty attains perfection.
Krishna teaches the importance of performing one's own duty. 'Sve sve karmaṇy abhirataḥ saṁsiddhiṁ labhate naraḥ'—a person (naraḥ) attains (labhate) perfection (saṁsiddhim) by being devoted (abhirataḥ) to one's own duty (sve sve karmaṇi). 'Svakarma-nirataḥ siddhiṁ yathā vindati tac chṛṇu'—hear (śṛṇu) how (yathā) one devoted (nirataḥ) to one's own duty (svakarma) attains (vindati) perfection (siddhim). This is the key teaching: perfection comes not from performing someone else's duty, but from being fully devoted to your own duty, according to your nature. When you perform your own duty with devotion, you attain perfection. This sets up the detailed explanation of how performing one's own duty leads to perfection.