Deuteronomy 18:15-20, Psalm 111, 1 Corinthians 8:1-13, Mark 1:21-28
"as one having authority, not like the scribes" - Chris Haslam writes in his comments that the scribes would be knowledgeable, quoting scripture, but not have their own authority. Jesus, on the other hand, draws on scriptures, sure, but speaks for himself - his authority is from within.
Haslam also says that healers/magicians of the day would have done rituals/magic to cleanse the man of the demon. Since Jesus can do this with only spoken words, the people see that indeed he does have a different kind of authority.
Because of this deed, Jesus' "fame" begins to spread. Do you think this is what Jesus most wanted people to know about him? His casting out demons? Or would he have rather been famous for his teaching and message of love and grace for the least? I think Jesus was savvy - he got people talking and drew them so he could teach and touch them.