I know this undecaying, ancient one, the self of all things, being infinite and omnipresent. They declare that in him all birth is stopped, for the Brahma-students proclaim him to be eternal.

In plain words: The speaker says he knows this ancient one who never grows old, the Self of all things, endless and everywhere. Teachers of sacred knowledge say he is eternal, and that in him the cycle of being born again comes to an end.