C. F. Keil and Franz Delitzsch on Isaiah 41:29

Isa 41:29

This closing declaration of Jehovah terminates with similar words of wrath and contempt to those with which the judicial process ended in Isa 41:24. “See them all, vanity; nothingness are their productions, wind and desolation their molten images.” מעשׂיהם are not the works of the idols, but, as the parallel shows, the productions (plural, as in Eze 6:6; Jer 1:16) of the idolaters - in other words, the idols themselves - a parallel expression to נסכּיהם (from נסך, as in Isa 48:5 = massēkhâh, Isa 42:17). אפס און is an emotional asyndeton (Ges. §155, 1,a). The address is thus rounded off by returning to the idolaters, with whom it first started. The first part, vv. 1-24, contains the judicial pleadings; the second part, Isa 41:25., recapitulates the evidence and the verdict.