Chapter 2 · verse 38 · gita.yoga.org

Bhagavad Gita 2.38

सुखदुःखे समे कृत्वा लाभालाभौ जयाजयौ। ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि

Having made pleasure and pain, gain and loss, victory and defeat equal, engage in battle for the sake of battle; thus, you shall not incur sin.