God says in Malachi 3:3 that He "sits as a refiner and purifer of silver." Refining and purifying silver requires the silversmith to sit and watch the silver in the flame, waiting for the exact moment that the dross -- the impurities -- are gone, and he can see his reflection in the liquid metal. He watches the entire time, lest it stay in the flame too long. In the same way, God watches over us as He refines us in various fires of life.

http://www.clarion-call.org/extras/malachi.htm