Chapter V Sloka 16

}anen tu td}an< ye;a< naiztmaTmn>, 
te;amaidTyvJ}an< kazyit tTprm!.

jnena tu tadajna 
ye nitamtmana | 
temdityavajjna 
prakayati tatparam ( 5|16)||

But to those whose ignorance is destroyed by the knowledge of the Self, like the sun, knowledge reveals the Supreme (Brahman).

Commentary:

When ignorance, the root cause of human sufferings, is annihilated by the knowledge of the Self, this knowledge illuminates the Supreme Brahman or that highest immortal Being, just as the sun illumines all the objects of this gross, physical universe.

The ego (jiva) looking up to the Atman finds that ignorance is enveloping the Infinite. This ignorance is not in the Truth just as the clouds are never in the Sun. Self-forgetfulness gives the ego the false-notion that Spiritual Reality is enveloped by ignorance. Ehen this ignorance is removed, the Self becomes manifest, just as when the cloud moves away, the Sun comes to our recognition. When the ego redisovers the Self, it becomes the Self.