5th February 2012 Mark 1:29-39

Jesus Heals Many
As soon as they left the synagogue, they went with James and John to the home of Simon and Andrew.  Simon’s mother-in-law was in bed with a fever, and they immediately told Jesus about her.  So he went to her, took her hand and helped her up. The fever left her and she began to wait on them.  That evening after sunset the people brought to Jesus all the sick and demon-possessed. The whole town gathered at the door, and Jesus healed many who had various diseases. He also drove out many demons, but he would not let the demons speak because they knew who he was.

Jesus Prays in a Solitary Place
Very early in the morning, while it was still dark, Jesus got up, left the house and went off to a solitary place, where he prayed. Simon and his companions went to look for him, and when they found him, they exclaimed: “Everyone is looking for you!”  Jesus replied, “Let us go somewhere else—to the nearby villages—so I can preach there also. That is why I have come.” So he traveled throughout Galilee, preaching in their synagogues and driving out demons.

These same passages were provided by the Lectionary earlier this month but today they've come to the main Sunday service.  Obviously they're important enough to be heard twice.
 
I'm left feeling confused today by the fact that Jesus drove out many demons but wouldn't let them speak because they knew who he was.  What did Jesus think would happen?  
 
It makes perfect sense not to let demons talk, but the reason given here is confusing.  What was the issue with them not speaking because they knew him? 
 
I've spent some time looking through commentaries to no avail so I'm none the wiser today, perhaps someone knows and can tell me; for now it remains a mystery to me.
 
Father, I'm reminded today that much of your word is unclear to me; in this I fall back on my faith of you and that you will make clear what I need to know.  Thank you for teaching me to trust in you.  Amen.