The Hebrew verb tsaraph means to refine, smelt, or test metals by fire — particularly silver and gold. Used 33 times in the OT, it describes both the metallurgical process of purifying precious metals and God's divine work of refining His people through trials and suffering.
God uses tsaraph as a picture of spiritual purification. Just as a refiner heats metal to remove dross, God allows suffering and trials to remove sin and produce holy character. The image of the silver refiner watching until he sees his reflection in the molten metal is a powerful picture of God's goal: conforming His people to His image. This word underlies the theology of sanctification through suffering (Romans 5:3–4).