Proverbs 17:3 in the World English Bible
The refining pot is for silver, and the furnace for gold, but the LORD tests the hearts.
Context
2 A wise servant shall have rule over a son that causeth shame, and shall have part of the inheritance among the brethren.
3 The fining pot is for silver, and the furnace for gold: but the LORD trieth the hearts.
4 A wicked doer giveth heed to false lips; and a liar giveth ear to a naughty tongue.