Bhagwad Gita
Chapter 18, Verse 6
एतान्यपि तु कर्माणि सङ्गं त्यक्त्वा फलानि च।कर्तव्यानीति मे पार्थ निश्िचतं मतमुत्तमम्।।18.6।।
All these activities should be performed without any expectation of result. They should be performed as a matter of duty, O son of Prtha. That is My final opinion.