Know Self first then Supreme Self.

“Bright is he”

In the Katha Upanishad it is said of the self: “Him the sun does not illumine, nor the moon, nor the stars, nor the lightning
–nor, verily, fires kindled upon the earth.
He is the one light that gives light to all.
He shining, everything shines.”

The self is illumined by no external light, but rather illumines all itself.
We could shine the brightest of lights into the eyes of a dead man and he would see nothing. But if the self is present to enliven him, then he will.

The self is known–seen–by the self, and therefore it is called swayamprakash: self-illumined.

Hence only those in contact with their self can be said to possess illumination to any degree.
Those who under the banner of “devotion” obsess on external practices and deities can only dwell in the “light that is darkness.”

We must seek illumination in the self
alone, keeping in mind that God is the Self of the self, that to seek one is to seek the other.
Sukram, the word translated “bright,” also means pure in the sense of being of such perfect clarity that no light is obscured. For it is from the core of the self that the Pure Light of God shines forth.
Therefore, as just pointed out, to attain self-knowledge is to realize both the atman and the Paramatman. Only when we are centered in our self can we see God, and only when we are centered in God can we truly know our self.

In a flawless crystal, what do we see? Nothing. So also, in the self there is nothing seen, for all “things” are transcended, and pure Being alone remains in our consciousness.

Wherefore the Chandogya Upanishad tells us:
“Where one sees nothing but the One, hears nothing but the One, knows nothing but the One
–there is the Infinite.
Where one sees another, hears another, knows another
–there is the finite.
The Infinite is immortal, the finite is mortal.”

– Commentary on the Isavasya Upanishad–by Swami Nirmalananda Giri.