Everything that is hidden will be made visible...for a lamp's place is the lampstand. Today's Gospel reading is a follow up of the Parable of the Sower that was the content of yesterday’s Gospel reading. If yesterday's reading left the apostles lost, I bet today's follow up doesn't fare any better. What is this that has been hidden? Is there a lamp that has not been put to its proper use? 
Jesus began his ministry by proclaiming the time of fulfillment, that is, the in-breaking of the kingdom of God. The beginning of Jesus' ministry inaugurates the fulfillment of the promises God has made to God's people through Israel. It is in Jesus that these promises are to be fully realized because Jesus is the full revelation of God.
Israel had been chosen by God as the recipient of God's revelation. As the elected nation, Israel was to be a means of God’s blessing upon other nations (cf. Gen 12:2), as well as being a light to the nations (cf. Isaiah 42:6). Israel was to lead the nations to the knowledge of God through her godly actions ( opening eyes of the blind and freeing captives from prison and dark dungeons [cf. Isaiah 42: 7]). This is where Jesus picked up from when he began his public ministry (cf. Luke 4:16ff). Jesus presented his life and ministry as the coming to fulfillment of God's promises. The revelation that had been limited to Israel until this moment was now made accessible to all. The knowledge of God that had been limited to Israel was now made accessible to the nations. The knowledge to salvation that had been hidden from the nations was now made accessible to them. In Jesus, Israel was now taking her place in the lampstand as the light to the nations.