Jeremiah 11:3 - Ellicott's Commentary On The Whole Bible

Cursed be the man... — The verse is, as it were, a mosaic, so to speak, of phrases, with slight verbal changes, from the recently discovered book of Deuteronomy — the “iron furnace” from Deuteronomy 4:20; 1 Kings 8:51, “Hear my voice and do them” from Deuteronomy 28:1, “Ye shall be my people” from Deuteronomy 29:13. The “iron furnace” was, of course, Egypt, the “furnace of affliction,” as in Isaiah 48:10, in which the people had endured sufferings of which that was the only adequate symbol. The word used denoted the “furnace” of the smelter, but the actual form of bondage through which the Israelites had passed, working in the brick-kiln furnaces (Exodus 1:14), had probably given a special force to the phrase.