words = the spoken words, sayings, or utterances. Compare Psa_119:38.
silver tried: i.e. pure silver.
furnace = crucible. Put a full stop after this word.
of = to, or pertaining to (referring to the "words"). The letter lamed is the sign of the Dative case, not the Genitive.
earth. Hebrew. 'erez (the earth), not 'adamah (the ground): i.e. "words for, or pertaining to the earth", but purified seven times: i.e. with spiritual perfection (see App-10). Some are used with a higher meaning; some in a different sense. Psa_12:6 is an alternation.
Purified. The verb is singular, agreeing with silver. The words of Jehovah are pure words. As silver tried in a furnace: [Words] pertaining to the earth: Purified seven times.