Charles Ellicott Commentary Psalms 12:6

"The words of Jehovah are pure words; As silver tried in a furnace on the earth, Purified seven times." — Psalms 12:6 (ASV)

As silver: This solemn promise of Jehovah can be relied upon, for His words are not like those of deceitful men—alloyed with self and falsehood—but are pure as silver seven times smelted.

In a furnace: This refers to either a “workshop” or a “crucible,” depending on its derivation.

Of earth: These words are difficult. They must mean either in earth, referring to the ashes in which the smelted silver falls, or as to earth, that is, as to the alloy, or, as we might say, purified of the alloy.

But erets is not used elsewhere for the material, earth, and Hitzig’s emendation, rats = bar, or piece (Psalms 68:30), “melted into a bar from the crucible,” is almost convincing in its simplicity and aptness.