The words of the Lord - In contrast with the words of the persons referred to in Psalms 12:2-4. Their words were vanity, flattery, and falsehood; and no reliance could be placed on them. In contrast with these words, the words of the Lord were pure. They were to be relied on. All his sayings were true and faithful. The design is to bring his words into contrast with the sayings of such men, and to show how much more safety there is in relying on his promises than on the promises made by such men. Man failed, but God would not. Reliance could not be placed on the words of even the professedly “godly” and “faithful” Psalms 12:1, but entire confidence might be placed in the words of Yahweh. All his words were true, pure, faithful, so that even when his own professed friends failed, and confidence could be placed in them, yet there was still reason for unwavering confidence in God himself.
Are pure words - That is, they are without any mixture of falsehood - for this idea is implied in the comparison which the psalmist makes when he says that they are like silver purified in the furnace, that is, from which all the dross has been removed.
As silver tried in a furnace of earth - The word here rendered “furnace” properly means a workshop. Perhaps it corresponds nearly with our word “laboratory,” as the term is now used by chemists. It evidently refers to some place where the metal was tried and purified. The words rendered “of earth” literally mean “on the earth,” or “in the earth?” The language does not mean that the “furnace” was “made” of earth, as would seem to be implied in our version, but that the “furnace” or laboratory was erected on the earth, or in the earth. It may refer to something like a crucible placed on the ground, around which a fire of intense heat could be made. It is probable that some such structure would be made near the mines where ore was obtained, and that the ore would be thus purified from dross before it was removed.
Purified seven times - By passing it seven times - that is, very often - through the fire. The word “seven” in the Scriptures denotes a complete or perfect number, and is often used to denote frequency. The idea here would seem to be that the process was repeated until the silver became entirely pure. The sense is, that the words of the Lord are “perfectly pure.” There is no admixture of falsehood in his statements; there is no deception in his promises; there is no flattery in what he says. This was the ground of confidence on the part of the psalmist - that while men (even those who professed to be good men) so failed that no reliance could be placed on their statements, the most perfect trust could be reposed on all the statements of God.