In plain words
As sunlight makes the world's activity possible, the Self enables mind and senses to function. Free of every limiting condition, it abides like space, always itself. I am that ever-established Self.
Word for word
As the sun is spoken of as the enabling cause of the world's activities, He enables the functioning of mind, eye and the other faculties. Free of all limiting adjuncts, He abides like space, of one nature, ever established. I am that Self.