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.
tn Heb “to be his people of inheritance.” The Lord compares his people to valued property inherited from one’s ancestors and passed on to one’s descendants.