Albert Barnes Commentary Mark 1:27-28

"And they were all amazed, insomuch that they questioned among themselves, saying, What is this? a new teaching! with authority he commandeth even the unclean spirits, and they obey him. And the report of him went out straightway everywhere into all the region of Galilee round about." — Mark 1:27-28 (ASV)

And they were all amazed, etc. The power of casting out devils was new to them. It was done by a word. He did it in his own name, and by his own authority. This proved that he was superior to all the unclean spirits. In consequence, his fame spread throughout all the country, and the impression became prevalent that he was the Messiah.