"You are the light of the world; you cannot hide a city built on a hill; - Nor does the lamp light and stand under the bushel, but on the lampstand, and give light to everyone in the house. - your light before men, that they may see your good works and glorify your Father who is in heaven. "
(Matthew 5: 14-16)
In order for our light to shine before men, we must first let the light of God shine on the dark places of our hearts, bringing out all hidden sin, and all the dirt that lurks in the darkness. It is often painful to see truths about us, but when God brings the light that needs to be transformed, it is so that He can cleanse us and make us free from everything that holds us and keeps us from Him. When we do not let God shine His light in our hearts, it is as if we hide our light under the bed. But when we allow Him to shed light in our darkness, as the psalmist prays, then our light will shine before men, and what people will see will be good works, because they are done with a pure heart, for the glory of God.