The ambiguity in Isa 54:16a concerning the identity of the subject (Yhwh or the smith) of the two verbs relating a metallurgical action (to blow and to cast) is identified here as a rhetorical device intending to conceal the essential relation of YHWH with metallurgy. Integrated in the whole Isa 54 chapter, this device becomes a plea for the definitive replacement of Edom with Israel as yhwh 'speople, exactly as in Isa 34-35 and Isa 61-63.