B.G 2.38

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

sukhaduḥkhe same kṛtvā lābhālābhau jayājayau। tato yuddhāya yujyasva naivaṃ pāpamavāpsyasi ॥2-38॥

[सुख (sukha) - happiness; दुःखे (duḥkhe) - distress; समे (same) - in equanimity; कृत्वा (kṛtvā) - having made; लाभ (lābha) - gain; अलाभौ (alābhau) - loss; जय (jaya) - victory; अजयौ (ajayau) - defeat; ततः (tataḥ) - then; युद्धाय (yuddhāya) - for the sake of fighting; युज्यस्व (yujyasva) - engage; न (na) - not; एवं (evaṃ) - thus; पापम् (pāpam) - sin; अवाप्स्यसि (avāpsyasi) - you will incur;]

(Treat happiness and distress, gain and loss, victory and defeat with equanimity. Then engage in battle, and you will not incur sin.)

Regarding pleasure and pain, gain and loss, victory and defeat with equanimity engage yourself in the battle, there by you will not incur sin.