The fining pot is for silver, and the furnace for gold: but the LORD trieth the hearts.
– Proverbs 17:3
On the face, this proverb is obscure, but the wisdom revealed is not too advanced for the Proverbs. The parallelism gives us what we need to discern the meaning. The fining pot and furnace refer to the crucible used for testing and purifying precious metals such as silver and gold. These images were used to speak of testing by trials God designs for the purifying of His own (Job 23:10; Psalm 66:10; Isaiah 48:10; 1 Peter 1:6-7). The second line goes deeper. It is the hearts, or the inner man, his thoughts, feelings, and motives, which are tried (Proverbs 15:11). God’s testing is not of outward appearance but of internal thoughts and motives (Proverbs 24:12). So God tests with full knowledge and purpose to draw out the impurities of the heart as the refiner separates the dross from the metal.