Although this is the same illustration that is found in Matthew 5:15, Mark 4:21, and Luke 8:16-18, it is not the same occasion, and a different lesson is drawn from it. By including this illustration twice in different contexts, Luke shows us that the Lord was happy to use the same illustration in two different ways.
The first thing about this lamp is that it attracts people to its light, and that is the same with Jesus Christ and the message of the gospel. This is first and foremost an amazingly attractive and appealing message, or it ought to be to us. It is attractive and appealing because it is speaking about the most amazing, the most wonderful gift we could ever receive. This is about receiving eternal life, everlasting life. This is about having all our sin blotted out from the presence of God. This is about receiving a new life with which we can relate to Almighty God and know him and speak with him. There is nothing to touch this on the face of the earth. When you hear this teaching – ‘Come unto me and I will wash away your sins. I have come from heaven to earth to suffer and die to take your punishment for you, and I will give you new life, and I will bring you everlastingly to the heavenly glory’ – it should draw you to him. We have to talk about sin; we have to talk about our guilt; we have to warn that everyone that we must repent and come to him and yield our lives to him. We have to convince people that they are sinners and that they have this mountain of guilt which will condemn them eternally. Almighty God owes us nothing, and by rights should condemn us all. But he looks down from heaven and says, ‘Why will you die? Come and have your sins forgiven and have a new life.’
It's about coming in. As we are born by nature, we're outsiders and yet we can become insiders. You come to this light and you learn from this message you can become an insider. You can know and understand things which you were never privy to before; you can know God and learn about him, and about his plans and his ways. Those who are familiar with the Lord, who walk with him and know him, come in and see the light. The ministry of Jesus Christ shows us how to get to God, how to approach him, how to speak with him, how to receive his blessing.