'Om tat sat', this is the threefold designation of Brahman, so handed down and so contemplated by the knowers of Brahman in the Upanishads. A designation is that by which a thing is pointed out. By this threefold designation the brahmins, the Vedas, and the sacrifices were of old fashioned and brought into being; this is said in praise of the designation.

'Om tat sat', this threefold designation, this word, is remembered as belonging to Brahman; it is connected with Brahman. And Brahman is the Veda; by the word 'Veda', Vedic action is meant; the Vedic action, sacrifice and the rest, becomes connected with the word 'sat'. The connection of the word 'Om' is by its being used at the beginning of the carrying out, as a subsidiary of Vedic action; the connection of the words 'tat' and 'sat' is, by being designators, for the sake of holding it worthy of honour. Joined with that threefold word, the brahmins, connected with the Veda, the men of the three classes, and the Vedas and the sacrifices, were of old set forth, were of old fashioned by Me alone. This is the meaning. The manner of the connection of the three words 'tat' and 'sat' is described. First the manner of the connection of the word 'Om' is told.

Again, to enjoin the manner in which action and the rest are to be done, Krishna speaks a passage of explanatory praise, with 'Om tat sat' and so on. For these are the names of the supreme Brahman. The supplementary hymns of the Rigveda say, 'in whom the world is woven, and who is Himself full, of the form told in the Veda and without figurative usage, joined with all that is auspicious and with nothing else, Him they therefore call by the words tat sat'. The second line gives the meaning of the word 'tat'. And there is 'the existent alone, my dear, was this in the beginning' (Chandogya Upanishad 6.2.1), and 'Om is Brahman' (Taittiriya Upanishad 1.8.1). By that Brahman the Vedic rule is a manifesting, for the sake of the worship of the Self. The pranava, Om, was spoken of before.