Let your light so shine before men, that they may see your good works and give glory to your Father who is in heaven. Matt. 5:16, R.S.V.
My friend Chuck works on a giant fusion research project. In massive buildings that cover acres of staggeringly expensive equipment, brilliant men are trying to reproduce the same process that happens inside the sun: the release of energy through atomic fusion.
In this project a tiny target is blasted with the energy of huge laser beams, focused through an array of unusual lenses. These lenses are made of a special plastic material designed specifically for laser energy levels. One of Chuck's jobs is to make sure that every one of the hundreds of lenses is spotlessly clean each time the target is fired upon. If there is so much as a tiny speck of dust on them, two things will happen: The first problem is that the tiny speck of dust will diffuse light, keeping it from reaching its target. Several pieces of dust will measurably cut down on the efficiency of the whole project. Thus it requires even more laser energy to create fusion in the target.
But the more serious problem is that the speck of dust that stops the light from going through the lens turns the light energy into heat energy. That heat leaves a tiny black burn mark on the lens. The next time that incredibly strong burst of light hits the lens, the tiny burn mark stops even more light, creating a still bigger scar. Before long, a single burst of light will instantly destroy the lens.
Francis Ridley Havergal, in a profoundly insightful hymn, suggested how Christians view themselves: "I, the transparent medium Thy glory to display." Perhaps she had been reading about the fourth angel of Revelation 18 who would lighten the earth with his glory. She knew that the word glory applied specifically to the knowledge of the character of God. And she knew that God wanted to use His people as the channels for such powerful truth about Himself to cover the whole earth.
I think that God is cleaning His lenses, for both the above reasons. He wishes for His gracious character to be known, without distortions, through the people who bear His name. And perhaps there is also a hint in this analogy of how the persistently rebellious will be destroyed by the same brightness that brings rejoicing to the righteous.