This psalm contrasts the language of the wicked, who speak duplicitously with a forked tongue, with the pure unadulterated words of God. To express the level of purity of Hashem’s words, the verse uses the metaphor of metal mined from the earth, which goes through seven stages of refinement in order to arrive at a level of purity worthy of a precious metal. It is not surprising that the psalmist would be aware of the process of metallurgy. Archaeology at Timna Park in southern Israel reveals evidence of copper mining going back thousands of years. In 1959, an archeo-metallurgical expedition under the leadership of Dr. Beno Othenberg began, and ultimately revealed over 10,000 copper mines in the southern Arava region of Israel. More contemporary discoveries date some of the mines to the eleventh to ninth centuries BCE, which coincides with the period of the Israelite kingdom.
Source: Israel in the News