Therefore, beginning with ‘Oṃ’, the actions of sacrifice, charity and austerity, ordained according to precept, proceed always for the speakers of Brahman.

Practical use of oṃ. The three main actions — yajña, dāna, tapas — begin with oṃ, the syllable that connects with Brahman.

Vidhānoktāḥ — said/regulated by the vidhāna (precept). Pravartante — proceed, are performed. Satatam — continuously, always. For brahma-vādinām — those who speak/express Brahman, those knowing it.