God is light (1 John 1:5).  That does not only mean that He has unlimited energy, but also that truth is His nature.  Jesus described himself as 'the light of the world' (John 9:5) bringing God’s truth into a swamp of lies and deception, self-interest and hatred.  In these verses He told His disciples that they are the light of the world!  Does that mean that they are God?  No!  But God's purpose is to share His nature and His mission with those who believe in Jesus (John 8:12), so that they can shine truth into a dark world (Philippians 2:14-16).

Jesus came to teach God's truth.  Blind people were physically healed (Luke 7:22); that was a prophetic sign that God would enable His Word to be revealed to people trapped in darkness (Isaiah 29:18).  But Jesus knew that He would soon place His mission, of announcing His saving grace to the world, in the hands of His disciples (Matthew 28:18-20).  They needed to be ready to be outward-facing, truth-declaring messengers.  They must not hide the truth from people but be bold and courageous to preach the gospel despite persecution (Matthew 24:9-14).

Light must be seen if it is to do its job.  It is pointless to light a lamp and then shut it away.  It must be set in a high place so that it cannot be obscured by other things.  Jesus was saying that His disciples needed to be obvious like a fortified hilltop city.  The light they had received was too valuable to be kept under cover.  Like John the Baptist, they were to be beacons of light to those who had lost their way. (John 5:35).   

Every believer in the Lord Jesus Christ is a light in the world.  That is our spiritual responsibility.  We are not here to make money, to enjoy ourselves, or to make a name for ourselves.  We are here to shine out truth and love for God and His world.  Like Jesus, we will find ourselves close to corruption in order to be God’s agent of transformation.  We will sing praise when others complain, work when others have given up, show compassion when nobody else cares and pray when everybody has given up hope.  Above that, we will explain to lost people how they can find Jesus, telling the gospel to those who are crushed.  It is not that we will be the light of the world; we already are.  So get shining today!