Bhagavad Gita Chapter 17, Verse 27

यज्ञे तपसि दाने च स्थितिः सदिति चोच्यते | कर्म चैव तदर्थीयं सदित्येवाभिधीयते ||

yajñe tapasi dāne ca sthitiḥ sad iti cocyate karma caiva tad-arthīyaṁ sad ity evābhidhīyate

Steadfastness in sacrifice, austerity, and charity is also called 'SAT,' and action performed for the sake of That (the Supreme) is also called 'SAT.'

Krishna explains the deeper meaning of SAT. 'Yajñe tapasi dāne ca sthitiḥ sad iti cocyate'—steadfastness (sthitiḥ) in sacrifice (yajñe), austerity (tapasi), and charity (dāne) is also called (ucyate) 'SAT' (sat iti). 'Karma caiva tad-arthīyaṁ sad ity evābhidhīyate'—and action (karma) performed for the sake of That (the Supreme) (tad-arthīyam) is also called (abhidhīyate) 'SAT' (sat iti eva). SAT means not just truth and goodness—it also means steadfastness in practice and dedication to the Supreme. When you practice with steadfastness and dedication to the Supreme, you practice SAT. Understanding this helps you recognize that SAT is both the practice itself (steadfastness) and the purpose (dedication to the Supreme).