Bhagavad Gita Chapter 17.26 - 17.27
sad-bhāve sādhu-bhāve ca
sad ity etat prayujyate
praśaste karmaṇi tathā
sac-chabdaḥ pārtha yujyate
yajñe tapasi dāne ca
sthitiḥ sad iti cocyate
karma caiva tad-arthīyaḿ
sad ity evābhidhīyate
Translation The Absolute Truth is the objective of devotional sacrifice, and it is indicated by the word sat. The performer of such sacrifice is also called sat, as are all works of sacrifice, penance and charity which, true to the absolute nature, are performed to please the Supreme Person, O son of Pritha.