http://www.ccel.org/ccel/mcgarvey/gospels.vi.xiii.html
But he said unto them, I must preach the good tidings of the kingdom of God to the other cities also: for therefore was I sent.
Jesus is still in Capernaum. There is much work to be done there, and the disciples are anxious for Jesus to get to work healing and performing miracles. But Jesus knows that his primary task is not miracle-working, it is preaching the good news of reconciliation with God. So rather than rest on his fame in Capernaum, he travels throughout Galilee preaching and teaching and healing.