Bhagavad Gita Chapter 17, Verse 26

सद्भावे साधुभावे च सदित्येतत्प्रयुज्यते | प्रशस्ते कर्मणि तथा सच्छब्दः पार्थ युज्यते ||

sad-bhāve sādhu-bhāve ca sad ity etat prayujyate praśaste karmaṇi tathā sac-chabdaḥ pārtha yujyate

The word 'SAT' is used in the sense of Truth and goodness, and also in praiseworthy actions, O son of Pritha.

Krishna explains how SAT is used in spiritual practices. 'Sad-bhāve sādhu-bhāve ca sad ity etat prayujyate'—the word SAT (sat iti etat) is used (prayujyate) in the sense of Truth (sat-bhāve) and goodness (sādhu-bhāve). 'Praśaste karmaṇi tathā sat-śabdaḥ pārtha yujyate'—also (tathā) in praiseworthy (praśaste) actions (karmaṇi), the word SAT (sat-śabdaḥ) is used (yujyate), O son of Pritha (pārtha). SAT means Truth, Existence, and Goodness. When you use SAT, you affirm that your actions are true, good, and praiseworthy. SAT sanctifies actions by connecting them to Truth and goodness. Understanding this helps you recognize the importance of SAT in affirming the truth and goodness of your actions.