O Pûshan, only seer, Yama (judge), Sûrya (sun), son of Pragâpati, spread thy rays and gather them! The light which is thy fairest form, I see it. I am what He is (viz. the person in the sun).

In plain words: The speaker keeps praying to the sun, calling it Pushan, the one seer, Yama the judge, Surya the sun, and child of Prajapati the creator. He asks it to pull back its blinding rays so he can see its most beautiful light. Then he realizes that the person within the sun is the same as himself.