The fining pot is for silver, and the furnace for gold. The word matsreph, "fining pot," occurs also in Proverbs 27:21. It is not certain what is meant by it. There is no evidence that the Israelites were acquainted with the use of acids in the manipulation of impure or mixed metals; otherwise the "pot" and the "furnace" would represent the two usual modes of reduction; but it is most probable that both allude to the same method of smelting the ore in crucibles, for the purpose of separating the pure metal from the dross.
That silver and gold were plentiful in Solomon's time is abundantly evident; indeed, the amount of the precious metals collected by David and his son is almost incredible (see 1 Chronicles 22:14; 1 Chronicles 29:2, etc; from which and similar passages it is inferred that the sums enumerated equalled more than nine hundred millions of pounds sterling).
But the Lord trieth the hearts (Proverbs 15:11; Proverbs 24:12). That which fire does for the metals, the Lord does for men's hearts; he purifies them from dross, brings forth the good that is in them, purged from earthly infirmities.
God's process is the application of sorrow, sickness, temptation, that, duly meeting these, the soul may emerge from the trial as pure gold, fit for the Master's use (comp. Jeremiah 12:3; Malachi 3:2; 1 Peter 1:7; Revelation 3:18).