¹ tn A כּוּר (kur) was not a source of heat but a crucible (“iron-smelting furnace”) in which precious metals were melted down and their impurities burned away (see I. Cornelius, NIDOTTE 2:618-19); cf. NAB “that iron foundry, Egypt.” The term is a metaphor for intense heat. Here it refers to the oppression and suffering Israel endured in Egypt. Since a crucible was used to burn away impurities, it is possible that the metaphor views Egypt as a place of refinement to bring Israel to a place of submission to divine sovereignty.