Bhagavad-gītā 17.23
BG 17.23
Open the full passageॐतत्सदिति निर्देशो ब्रह्मणस्त्रिविधः स्मृतः । ब्राह्मणास्तेन वेदाश्च यज्ञाश्च विहिताः पुरा ॥२३॥
Sanskrit
oṁ tat sad iti nirdeśo brahmaṇas tri-vidhaḥ smṛtaḥ brāhmaṇās tena vedāś ca yajñāś ca vihitāḥ purā
Translation
From the beginning of creation, the three words oṁ tat sat were used to indicate the Supreme Absolute Truth. These three symbolic representations were used by brāhmaṇas while chanting the hymns of the Vedas and during sacrifices for the satisfaction of the Supreme.