Verse three of our chapter presents a conceptual context for the virtues promoted in Biblical wisdom literature, including the immediate blessings and character traits endorsed by Solomon in Proverbs 17.  Testing, tempering, & purifying are in view here as uses for heat in processing precious metals.  This analogy serves well to illustrate the design and redemptive purpose of life’s trials, difficulties, conflicts, hardships, suffering etc.. Carrying over the theme of divine sovereignty from chapter 16, the literary context of this verse provides a big picture perspective of divine purpose redeeming the hardships of life for the believer.  If the trials of life are the refining crucible or furnace, the character traits endorsed by Solomon in chapter 17 (as well as the entire book) are the refined treasure believers are promised as they submit to the providence of God in the challenges of life.