Jesus did not need to shout or use magic words. He spoke with the authority of the Son of God, and the evil spirit obeyed (1:1).
Be silent!: Jesus commanded the evil spirit not to reveal his identity. This is an example of the “messianic secret.” This term describes places in Mark where Jesus tells demons or people not to reveal who he is (1:25, 34; 3:11–12; 8:30; 9:9).