Thomas Aquinas

The smith. Here he shows their worthlessness, that not only are they not gods, but even worthless things. And first, he sets out the manner of their formation as to idols made from metal: with the strength of his arm, that is, striking strong blows; he shall hunger and faint, as if to say: the god which he is making cannot help him, although it is especially bound to its maker, above: the coppersmith striking with the hammer (Isa 41:7).

Commentary on Isaiah ↗