Bhagavad Gita 2.38

सुखदु:खे समे कृत्वा लाभलाभौ जयाजयौ |
ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि

Translation

Fight for the sake of duty, treating alike happiness and distress, loss and gain, victory and defeat. Fulfilling your responsibility in this way, you will never incur sin.