'Now that serene being which, after having risen from out this earthly body, and having reached the highest light (self-knowledge), appears in its true form, that is the Self, thus he spoke (when asked by his pupils). This is the immortal, the fearless, this is Brahman. And of that Brahman the name is the True, Satyam,

In plain words: The teacher says the calm being that rises from the body and shows its true form in the highest light of self-knowledge is the Self. It is deathless and without fear. It is Brahman, and its name is Satyam, which means 'the True.'