। ॥ २० ॥
In plain words
Every means of knowing leans on it; it leans on none. That is the word of the Veda, and that is what is accepted as the authority for knowing Brahman as the Self.
Close to the Sanskrit
That which is depended upon by all the means of knowledge, [and] which does not itself depend upon any means of knowledge — that word of the Veda is held to be the means of valid knowledge in the realization of Brahman as the Self.