He, the highest Person, who is awake in us while we are asleep, shaping one lovely sight after another, that indeed is the Bright, that is Brahman, that alone is called the Immortal. All worlds are contained in it, and no one goes beyond. This is that.

In plain words: The highest Being stays awake inside us even while we sleep and creates our dreams. That is Brahman, the Immortal. All worlds rest in it, and nothing goes beyond it.