Luke 8:16-18 (ESV)
“No one after lighting a lamp covers it with a jar or puts it under a bed, but puts it on a stand, so that those who enter may see the light.  For nothing is hidden that will not be made manifest, nor is anything secret that will not be known and come to light.  Take care then how you hear, for to the one who has, more will be given, and from the one who has not, even what he thinks that he has will be taken away.”
This teaching of Jesus has two primary applications. Jesus is first of all talking about the end of the world when all things will be brought to light. When Jesus returns nothing will be able to be hidden. People will have to give account. But it is not wrong to also see in this teaching here that as light is meant to pierce the darkness, so we who know Jesus are meant to shine into a very dark world so that Jesus Himself will be seen and embraced.
Believers in Jesus Christ are the light of the world and that light is not meant to be hidden so that it cannot be seen. When lights are covered up then darkness remains. We are called to shine as lights in a dark world (Philippians 2:14-16). God has lit the lamp and He has put us on display in the world so that we will shine and give light to the world. He has not saved us just so that we will celebrate the light and at the same time hide away with it so that the world is still in the dark. We are to shine as lights so that the Light may be seen. Our purpose is to show the world Jesus Christ. It is to demonstrate a great God.
We show Christ in our speech (Acts 8:4), and in our lives (I Peter 2:9-12). Our lives, even when we are persecuted and opposed in various ways are to demonstrate Christ (I Peter 3:15). Our hearts should be moved with compassion to those who do not know Him. The day is coming when all their deeds and hearts will be exposed (verse 17) and they must give account. It is a horrifying thought to think that people will stand before this great God without the benefits of Christ’s sacrifice between them and the righteous Judge.
Give people the Gospel. And give it with much prayer that the Father of mercies and God of all comfort (II Corinthians 1:3) will do a great work of saving power in them. Be in prayer regarding your own testimony at work, in school, at home, in social settings and in places of business. Pray to recognize the opportunities that God puts in your pathway for witnessing about the Gospel – for He does give you such opportunities. Pray to have people put in your path whom God is calling to Himself; that you will be used by God to bring them into the fold of grace. Pray to shine as lights as you are called to do.
This teaching ends with a great and solemn promise. Those of us who have the Gospel, if we use the knowledge that God has given us, will be given more to use as well. Use what God has given you. Do not try to go beyond what you know but study to know more. God will give you more as you prove faithful with what He has already given. It is easy to grumble about what we lack. Use what you have and show the Lord that you can be trusted with more. Why should He if you already squander what you have? God is not so foolish as to give you more to waste. Be faithful in a few things and He will bless you with greater.