Jesus was criticised for being obvious, outspoken, and direct.  His miracles attracted a lot of admiration, but His explanations fuelled accusation and condemnation.  Nobody minded Him healing, feeding them or even casting out demons; but they, and especially the religious leaders, resented His claim to be God's Messiah with a greater authority than them.  But wherever He went Jesus was the Light of the world whose presence revealed the thoughts and intentions of people’s hearts (John 8:12).

Jesus uses this story to show that there is no point in having a light unless it illuminates.  To keep an oil lamp under an opaque bowl is stupid.  Likewise, when the Light of the World arrived, He needed to be clearly seen, and then His light would show people what they needed to see.

The truth is that this sinful world is a very dark place: spiritually dark, a place where people cannot see what they are doing and do not know where they are going (John 3:19-21). Jesus came to do battle with the prince of darkness, who had been holding the world hostage under his evil spell (1 John 3:8). Wherever Jesus went, He 'switched the light on' for all those who wanted to see the truth and find a right relationship with God. That was His purpose.

And it still is.  But instead of Jesus being physically obvious, that role has been delegated to all those who believe in Him. Philippians 2:15 changes the scale of the analogy - from one light in a house to all the stars in the sky, "... so that you may become blameless and pure, ‘children of God without fault in a warped and crooked generation.’ Then you will shine among them like stars in the sky".  If Christ is in you then the light should shine wherever you go: to work, home, church or travelling in between.  The light is to shine so that those in darkness will be able to see the way to God, and fullness of life and look confidently towards eternity (Matthew 5:16).  Failure to do so is to frustrate part of God's purpose in giving you life and salvation.  We are not saved just for our own benefit but also so that others can see truth lived out in our lives, stimulating them to seek the Saviour too.