मयि सर्वाणि कर्माणि संन्यस्याध्यात्मचेतसा। निराशीर्निर्ममो भूत्वा युध्यस्व विगतज्वरः ॥

mayi sarvāṇi karmāṇi sannyasyādhyātma-chetasā nirāśhīr nirmamo bhūtvā yudhyasva vigata-jvaraḥ

Surrendering all actions to Me, with thy thoughts resting on the supreme Self, from hope and egoism freed, and of mental fever cured, engage in battle.

In plain words: Krishna tells Arjuna to offer all his actions to him and keep his mind on the highest Self. Free of selfish hopes, ego and anxious feverish worry, he should fight.