'Unclean Spirits' in the Bible

And they were all in astonishment, so that they questioned one another, saying, What is this? what is this new doctrine? that with authority he commands even the unclean spirits, and they obey him?

And the unclean spirits, when they beheld him, fell down before him, and cried out saying, Thou art the Son of God.

And immediately Jesus permitted them. And the unclean spirits going forth, entered into the swine; and the herd rushed violently down a precipice into the sea (they were about two thousand), and were suffocated in the sea.

And called the twelve, and began to send them two and two, and gave them authority over unclean spirits.