Metal-workers were common in the ancient world, and used their skills in a variety of ways (Gen 4:22; Exod 31:4; Judg 17:4; Isa 41:7; 44:12; 54:16). If they wanted to obtain pure metals from the raw materials they worked with, they first of all had to refine the metals. This was particularly so in the case of precious metals such as silver and gold (1 Chron 28:18; Mal 3:2-3). The metal was placed in a fire of intense heat so that, as the metal melted, impurities could be removed. The refining process tested and purified the metal. It was a vivid picture of the way God tests and purifies his people through the sufferings and hardships they experience (Ps 66:10; Prov 17:3; Isa 1:25; 48:10; 1 Peter 1:7; see TESTING).