17:27
यज्ञे तपसि दाने च स्थितिः सदिति चोच्यते ।
कर्म चैव तदर्थीयं सदित्येवाभिधीयते ॥१७- २७॥
yadnye tapasi daane cha sthitiH saditi chochyate ।
karma chaiwa tadarthiiyaM sadityewaabhidhiiyate ॥१७- २७॥
Source: Automatic ITRANS Transliteration
In sacrifice, austerity, and charity, steadfastness is articulated as "sat."
And even action toward that end is expressed as "sat."
Source: Milind S. Pandit
Faith in sacrifice, charity, and austerity is also called SAT. The action for the sake of the Supreme is verily termed as SAT.