yasya deve parā bhaktir yathā deve tathā gurau tasyaite kathitā hy arthāḥ prakāśante mahātmanaḥ

The purport of this verse is that one who is unflinchingly devoted to the Supreme Personality of Godhead, Visnu, and similarly devoted to the spiritual master, with no ulterior motive, becomes a master of all knowledge. In the heart of such a devotee, the real essence of the Vedic knowledge becomes manifest. This essence is nothing but surrender unto the Supreme Personality of Godhead (vedais ca sarvair aham eva vedyah). Only unto one who fully surrenders to the spiritual master and the Supreme Lord does the essence of Vedic knowledge become manifest, not to anyone else. This same principle is emphasized by Sri Prahlada Maharaja in Srimad-Bhagavatam (7.5.24):