Bhagavad Gita 2.38 Chapter 2, Verse 38

सुखदुःखे समे कृत्वा लाभालाभौ जयाजयौ ।
ततो युद्धाय युज्यस्व नैवं पापमवाप्स्यसि ॥२.३८॥

sukhaduḥkhe same kṛtvā lābhālābhau jayājayau
tato yuddhāya yujyasva naivaṃ pāpamavāpsyasi

Meaning

Treating pleasure and pain, gain and loss, victory and defeat alike, engage in battle. In this way you will incur no sin.

Newly written by Bhajan Dhun — scholarly review in progress.

Reference: Bhagavad Gita 2.38 (Chapter 2, The Yoga of Knowledge (Sankhya Yoga), Verse 38)