Bhagavad Gita: Verse 2.38
सुखदुःखे समे कृत्वा लाभालाभौ जयाजयौ ।
ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि ॥ २-३८॥
sukhaduḥkhe same kṛtvā lābhālābhau jayājayau
tato yuddhāya yujyasva naivaṃ pāpamavāpsyasi
Having made — pleasure and pain, gain and loss, victory and defeat — the same, engage in battle for the sake of battle; thus you shall not incur sin.
sukha = happiness; duḥkhe = and distress; same = in equanimity; kṛtvā = doing so; lābhālābhau = both profit and loss; jayājayau = both victory and defeat; tataḥ = thereafter; yuddhāya = for the sake of fighting; yujyasva = engage (fight); na = never; evaṃ = in this way; pāpaṃ = sinful reaction; avāpsyasi = you will gain.;