The first miracle in the Gospel of Mark is an exorcism and is the text for today. At the beginning of this pericope we are informed that Jesus taught in the synagogue with authority and the crowds were astounded at his teaching. Mark then immediately narrates the exorcism story to give a practical example of the teaching of Jesus. The demon "knows" who Jesus is and also that with his coming Satan’s reign is ended. Jesus has indeed come to cast Satan out.
The exorcism indicates what it means that the kingdom has indeed drawn near. This is the first time in the Gospel of Mark that we come across what is commonly known as “the command to silence”, which is a technique that Mark uses in his Gospel in which Jesus commands sometimes demons (1,25. 34), sometimes those he has healed (1,44) and sometimes the family members of the one healed (5,43) not to make known his identity or that he has been the one who has healed them. While many interpretations have been offered as to why Mark has used this technique, the one which has found wide acceptance is that the Marcan Jesus did not want people to mistake him for merely an exorcist or miracle worker, but wanted them to realise that he was the Christ who would suffer, die on the cross and be raised.
In this case he is able to exorcise the demon by a mere word, which the crowd interpret as a "new teaching".
By associating the teaching of Jesus with the first miracle and having the people regard the exorcism as a “new teaching”., Mark seems to want to indicate that there is no dichotomy between Jesus’ words and actions. They synchronise. Jesus does what he says and says what he does.