The story is told of a man who wanted to learn more about the process of refining silver. He called up a silversmith and made an appointment to watch him at work. The man didn't mention anything about the reason for his interest in silver beyond his curiosity about the process of how it was refined and made pure.
As he watched, the silversmith held a piece of silver over the fire and let it heat up. The silversmith explained that in refining silver, one needed to hold the silver in the middle of the fire where the flames were hottest, so as to burn away all the impurities.
As this was being done there in front of him, the man thought about God holding us in such a hot spot. His mind then went to the verse in Malachi chapter 3, where we’re told that God "sits as a refiner and purifier of silver." The man asked the silversmith if it was true that he had to sit there in front of the fire the whole time the silver was being refined.
The silversmith answered that yes, he not only had to sit there holding the silver, but he had to keep his eyes on the silver the entire time it was in the fire. If the silver was left even a moment too long in the flames, it would be destroyed.
The man was silent for a moment. Then he asked the silversmith, "How do you know when the silver is fully refined?" The silversmith simply replied, "When I see my image in it."