Bhagavad-Gita:

Also this is said to be

the light of lights
That is beyond darkness;
It is knowledge,
the object of knowledge
and that which is to be
attained through knowledge.

It is seated in the hearts of all...
For I am the foundation of Brahman,
Of the Immortal and the Imperishable,
And of everlasting virtue,
And of absolute bliss.