tn The Hebrew term כּוּר (kur, “furnace,” cf. Akkadian kūru) is a metaphor for the intense heat of purification. A כּוּר 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). Thus Egypt served not as a place of punishment for the Israelites, but as a place of refinement to bring Israel to a place of submission to divine sovereignty.
snFrom the middle of the iron-smelting furnace. The metaphor of a furnace suggests fire and heat and is an apt image to remind the people of the suffering they endured while slaves in Egypt.