2:38  

सुखदुःखे समे कृत्वा लाभालाभौ जयाजयौ ।
ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि ॥२- ३८॥

sukhaduHkhe same kRRitwaa laabhaalaabhau jayaajayau ।

tato yuddhaaya yujyaswa naiwaM paapamawaapsyasi ॥२- ३८॥

Source: Automatic ITRANS Transliteration

Having made happiness and suffering, profit and loss, victory and defeat the same,
Then join the war. So, you will not incur sin.

Source: Milind S. Pandit

Treating pleasure and pain, gain and loss, victory and defeat alike, engage yourself in your duty. By doing your duty this way you will not incur sin.

Source: The Bhagavad-Gita: The Sacred Song

Do thou fight for the sake of fighting, without considering happiness or distress, loss or gain, victory or defeat--and, by so doing, you shall never incur sin.

Source: Bhagavad Gita As It Is