Chapter II · Śloka 47
कर्मण्येवाधिकारस्ते मा फलेषु कदाचन |
मा कर्मफलहेतुर्भूर्मा ते सङ्गोऽस्त्वकर्मणि ||
मा कर्मफलहेतुर्भूर्मा ते सङ्गोऽस्त्वकर्मणि ||
karmaṇy evādhikāras te mā phaleṣu kadācana |
mā karma-phala-hetur bhūr mā te saṅgo 'stv akarmaṇi ||
mā karma-phala-hetur bhūr mā te saṅgo 'stv akarmaṇi ||
You have a right to perform your prescribed duties, but you are not entitled to the fruits of your actions. Never consider yourself the cause of the results of your activities, and never be attached to not doing your duty.
The most quoted verse of the Gita, and perhaps of all Indian scripture. Four negations, one affirmation: act — do not grasp the fruit, do not claim authorship of results, do not use wisdom as an excuse for inaction. In these three lines lives the entire path of karma yoga.