Shanti Parva 339.93

This great Upanishad quite of a piece with the four Vedas, and the Sankhya-Yoga, and called by him by the name of the Pancharatra Scriptures and recited by Narayana himself with his own mouth, was repeated by Narada before a large audience in the residence of Brahman (his sire) in exactly the same way in which Narayana had recited it and in which he had heard it from his own lips."