Bhagavad Gita 3.30
Therefore, surrender your actions to Me, keep your thoughts focused on the Absolute, free from selfishness and without expecting a reward, with a mind free from excitement, begin to fight.
मयि सर्वाणि कर्माणि संन्यस्याध्यात्मचेतसा।
निराशीर्निर्ममो भूत्वा युध्यस्व विगतज्वरः॥mayi sarvāṇi karmāṇi saṃnyasyādhyātmacetasā|
nirāśīrnirmamo bhūtvā yudhyasva vigatajvaraḥ||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).