1 Gita Sloka Every Day - Chapter 17 - Shraddhatraya Vibhaga Yoga - Sloka 23

The entire content of this mail is from Shri V N Gopala Desikan's  Srimad Bhagavad Gita, published by Vishishtadvaita Research Centre, Chennai and The Bhagavad Gita by Swami Chidbhavananda published by Ramakrishna Mission

Demerits Turned into Merits 23-28

1 Gita Sloka  Every Day - Chapter 17 - Shraddhatraya Vibhaga Yoga - Sloka 23

Om tat sat iti nirdeshah brahmanah trividhah smrutah I

Brahmanah tena vedah cha yagyah cha vihitah pura II sloka 23

ॐ तत् सत् इति निर्देशः ब्रह्मणः त्रिविधः स्मृतः I 

ब्रह्मणः तेन वेदः च यज्ञः च विहितः पुर II श्लोक 23

"Om Tat Sat" this has been declared to be the triple designation of the Brahman. By that were made of old the Brahmanas, the Vedas and the Yajnas. (23)

Every time a necessity arises for the indication of Brahman, these three words, Om Tat Sat are utilized either together or severally. Brahman projects Himself as sound for the purpose of manifesting Himself as the phenomenal universe. The sum total of the sound of the Cosmos is Om. It is otherwise called Nada Brahman. This sacred sound is interminable. Brahman is referred to by the utterance of Om. He is also indicated by the word Tat which means It. A respectable is not referred to by his name but with the simple word 'he'. In such deference, Brahman s indicated with the word 'It'. Again Sat means the Reality, which remains unaffected by time, space, and causation. Brahman is also referred to as Sat. This triple designation therefore always indicates Brahman. 

Though butter and buttermilk come from the same substance, milk, we only say that butter comes from milk and make no mention of the other substance. Though all things and being have come out from Brahman, the most prominent productions among them are the Brahmanas, the Vedas and the Yajnas. The most evolved and the most spiritually inclined ones among men are called the Brahmanas. Among the branches of knowledge, the sublimest are contained in the Vedas. And among the activities going on in the world, the most elevating and beneficial ones are the Yajnas. In the Nada Brahman, these three occupy the foremost place.