Page 42 (מב)
At 10 lines from the top of the page – (line begins: 'davkah...') For text, click: Here.
We are talking about the principle, 'the higher the light, in order for it to be manifest in the world it has to come to a low level'.
This has been illustrated by the comparison between the ox and the lion. Moses told the angels, 'you don't have an evil inclination and thus you cannot be the recipient of Torah'.
The light of Torah surfaces only by means of the birur/refinement of the evil inclination. This is where the truth of Torah is sensed.
On the first day there was light without a luminary. This is beyond our understanding. A ray of light from the sun is called a ha-arah/reflection. The light on the first day was the essence of light. It eliminated the darkness of the world, rather than illuminate it.
So too the light of torah. It can give you guidance/light of how to act in the world... but the basis of your behavior may be based on the presence of world. But the essence of torah is to transform this and make Him the basis of your behavior.
The evil inclination wants to focus purely on worldliness. It does not accept light in the world. It is bend on establishing worldliness as the basis. The Torah combats this on its turf. The supremacy of light comes from darkness.