Bhagavad Gita: Chapter 2, Verse 47

कर्मण्येवाधिकारस्ते मा फलेषु कदाचन ।
मा कर्मफलहेतुर्भूर्मा ते सङ्गोऽस्त्वकर्मणि ॥ २-४७ ॥

karmaṇy evādhikāras te mā phaleṣu kadācana
mā karma-phala-hetur bhūr mā te saṅgo ’stv akarmaṇi 2.47

You have a right to perform your prescribed duty, but you are not entitled to the fruits of action. Never consider yourself the cause of the results of your activities, and never be attached to not doing your duty.