Exodus 32:4. He received them at their hand, and fashioned it with a graving tool, after he had made it a molten calf.
Most of the large idols worshiped by the ancients were first made of wood and then covered with plates of metal. We find illustrations of this in Isaiah 30:22, and 40:19. See also Nahum 1:14; Habakkuk 2:18. A wooden image (or one of stone; see Hab. 2:19) was first prepared, and the gold was then cast into a flat sheet which the goldsmith hammered and spread out into plating which was fastened on the wooden form. Thus the goldsmith first melted the gold, and then used “a graving tool” to fashion it to the shape of the image. Aaron’s molten calf seems to have been made in this manner. “This is evident from the way in which it was destroyed: the image was first of burnt, and then beaten or crushed to pieces, and pounded or ground to powder (Deut. 9:21); that is, the wooden center was first burnt into charcoal, and then the golden covering beaten or rubbed to pieces; verse 20, compared with Deuteronomy 9:21” (Keil).
See further note on Isaiah 44:10 (#446).