Bhagavad Gita Chapter 18, Verse 23

नियतं सङ्गरहितमरागद्वेषतः कृतम् | अफलप्रेप्सुना कर्म यत्तत्सात्त्विकमुच्यते ||

niyataṁ saṅga-rahitam arāga-dveṣataḥ kṛtam aphala-prepṣunā karma yat tat sāttvikam ucyate

That action which is prescribed, performed without attachment, without desire and aversion, by one who does not desire fruits, is called sattvic.

Krishna begins explaining the three kinds of action, starting with sattvic action. 'Niyataṁ saṅga-rahitam arāga-dveṣataḥ kṛtam'—that action which is prescribed (niyatam), performed (kṛtam) without attachment (saṅga-rahitam), without desire and aversion (arāga-dveṣataḥ). 'Aphala-prepṣunā karma yat tat sāttvikam ucyate'—by one who does not desire fruits (aphala-prepṣunā), that action (yat karma) is called (ucyate) sattvic (sāttvikam). This is sattvic action: performing prescribed duty (yajña, dāna, tapaḥ) without attachment, without desire or aversion, without desiring fruits. This is the highest kind of action: duty-based, detached, balanced. You perform what you should perform (niyatam) because it's your duty, not because you're attached to it or want specific results. This is the path: duty without attachment to action or fruits, without desire or aversion.