Bhagavad Gita Chapter 17, Verse 17

श्रद्धया परया तप्तं तपस्तत्त्रिविधं नरैः | अफलाकाङ्क्षिभिर्युक्तैः सात्त्विकं परिचक्षते ||

śraddhayā parayā taptaṁ tapas tat trividhaṁ naraiḥ aphalākāṅkṣibhir yuktaiḥ sāttvikaṁ paricakṣate

That austerity which is practiced with supreme faith by people who do not desire results—that three-fold austerity is declared to be sattvic.

Krishna describes sattvic austerity—austerity that is sattvic. 'Śraddhayā parayā taptaṁ tapas tat trividhaṁ naraiḥ'—that austerity (tapas) which is practiced (taptam) with supreme faith (śraddhayā parayā) by people (naraiḥ), the three kinds (trividham). 'Aphalākāṅkṣibhir yuktaiḥ'—by those who do not desire results (aphalākāṅkṣibhiḥ), endowed (yuktaiḥ). 'Sāttvikaṁ paricakṣate'—it is declared (paricakṣate) to be sattvic (sāttvikam). Sattvic austerity is practiced with supreme faith, without desire for results, combining all three kinds (physical, speech, mental). It's not about getting something—it's about practicing discipline for its own sake, with faith and understanding. Understanding this helps you recognize and practice sattvic austerity.