The demons only heard the last part of the sentence, that they would be the rulers of the three worlds.
So as soon as the discourse was over,
the chief demon approached Brahma first and said :
"Father, please tell me, what is self-knowledge. Because I want to be the ruler of the three worlds."
And the Upanishad says that Brahma asked him to look at the mirror.
"What do you see there?" "I see myself," said the demon.
"That’s it," said Brahma. "You said so."
Do you understand the trouble of using language?
The Guru is supposed to impart self-knowledge, so he asks the disciple to look into the mirror.
"What do you see?" he says.
"I see myself," says the disciple.
"That’s it," says the Guru.
But then what is the disciple’s understanding of "that’s it?"
The demoniacal disciple’s understanding was that the body is the self.
Sri Swami Venkatesananda
To be continued ....