Bhagavad Gita 18.6

एतन्यपि तु कर्माणि सङ्गं त्यक्त्वा फलानि च |
कर्तव्यनिति मे पार्थ निश्चितं मतमुत्तमम्

Translation

These activities must be performed without attachment and expectation for rewards. This is My definite and supreme verdict, O Arjun.