तस्माच्छास्त्रं प्रमाणं ते कार्याकार्यव्यवस्थितौ ।ज्ञात्वा शास्त्रविधानोक्तं कर्म कर्तुमिहार्हसि ॥
tasmācchāstraṃ pramāṇaṃ te kāryākāryavyavasthitau |jñātvā śāstravidhānoktaṃ karma kartumihārhasi ||
Therefore, let scripture be your authority in deciding what should be done and what should not. Knowing what the injunctions of scripture declare, you should act accordingly here in this world.
Explanation
Krishna closes the chapter by drawing a conclusion from the previous verse, which said that acting on mere desire (kāma) leads to neither success nor happiness. He tells Arjuna to take scripture (śāstra) as his guide in deciding right action from wrong. Interpreters differ on what śāstra covers here: some stress the Vedic injunctions and rules of duty, while others read it more broadly as the Gita's own teaching on dharma, or as ethical guidance in general.