Albert Barnes Commentary Proverbs 17:3

"The refining pot is for silver, and the furnace for gold; But Jehovah trieth the hearts." — Proverbs 17:3 (ASV)

Wonderful as is the separation of the pure metal from the dross with which it has mingled, there is something yet more wonderful in the divine discipline which purifies the good that lies hidden, like a grain of gold, even in rough and common natures, and frees it from all admixture of evil. Compare Malachi 3:2; 1 Peter 1:7.