en_tn/pro/17/03.md

The crucible is for silver and the furnace is for gold

This refers to how gold and silver are refined. A metal is refined by heating it to a high temperature so that it melts and the impurities may be removed. Alternate translation: "The crucible is used to refine silver and the furnace is used to refine gold" (See: rc://en/ta/man/translate/figs-explicit)

crucible

a pot in which metals are melted at a very high temperature

Yahweh refines hearts

This speaks of Yahweh testing people to help them stop being evil and foolish as if their hearts were a metal that Yahweh was refining to remove everything that is impure. Alternate translation: "Yahweh tests peoples' hearts" (See: rc://en/ta/man/translate/figs-metaphor)