Bhagavad Gita Chapter 3, Verse 15

कर्म ब्रह्मोद्भवं विद्धि ब्रह्माक्षरसमुद्भवम् | तस्मात्सर्वगतं ब्रह्म नित्यं यज्ञे प्रतिष्ठितम् ||

karma brahmodbhavaṁ viddhi brahmākṣara-samudbhavam tasmāt sarvagataṁ brahma nityaṁ yajñe pratiṣṭhitam

Know that action arises from Brahman (the Vedas), and Brahman arises from the imperishable Supreme. Therefore, the all-pervading Brahman is eternally established in yajna.

Krishna reveals the metaphysical foundation: your actions aren't random—karma (action) arises from Brahman (cosmic order/Vedas), which arises from the imperishable Supreme. This means reality has an operating system, and it's based on yajna (reciprocity). The 'all-pervading Brahman is eternally established in yajna'—the deepest principle of existence is mutual nourishment, not extraction. When you act selflessly, you're not being virtuous; you're aligning with how reality actually works. This isn't moral philosophy; it's how existence operates.