Vidyaranya, aka Madhavacharya (not to be confused with the Dvaita philosopher Madhvacharya), was a famous Advaitin philosopher who was the Shankaracharya of Sringeri and the brother of Sayana, the famous commentator on the Vedas. (I wrote a fictional story about Vidyaranya here.) Vidyaranya helped found the Vijayanagara Empire, and he composed many famous works including the Sarvadarshana Sangraha (a summary of all philosophical schools) and the Panchadasi (a summary of Advaita). But my question is about another work of Vidyaranya, the Pranava Mimamsa, which is a work about significance and use of the syllable Om.
In this excerpt from the Pranava Mimamsa, Vidyaranya argues that when Hindu scripture says "pranavasya rishi Brahma", meaning "Of the syllable Om, the sage who heard it during meditation is Brahma", it's referring to the supreme Brahman, not to the creator god Brahma. Vidyaranya cites several scriptures to show that Brahma was not the seer of the syllable Om, rather Brahma learnt the Vedas along with Om from the supreme Brahman. In particular, he says this:
He, the incarnate power of Vishnu's intelligence, declares in the Satyavata:
"With the heart he extended Brahman to the first sage."
The meaning is as follows: "who", i.e. the Highest Self, "with the heart", i.e. mentally, "extended", i.e. explained, "Brahman", i.e. the Vedas, "to the first sage", i.e. to Hiranyagarbha.
Now I'm pretty sure the incarnation of Vishnu being quoted is Vyasa, for two reasons. First of all, "incarnate power of Vishnu's intelligence" seems like a translation of "Jnana-Shakti Avatara of Vishnu", which is an often-used appellation of Vyasa. Second of all, I assume "Satyavata" refers to the fact that Vyasa is the son of Parashara and Satyavati.
But my question is, what work of Vyasa is Vidyaranya quoting here? Vyasa is the author of the Mahabharata, the Puranas, and the Brahma Sutras, as well as the compiler of the Vedas. Now if a work was called by the appellation "Satyavata", it seems to me that it would probably refer to the Mahabharata.
But does anyone know if this verse occurs in the Mahabharata or any other scripture? The translator says "I have not been able to identify the verse." If it helps, the verse is given in Sanskrit here; it's verse 47.