Charles H. Spurgeon on Psalms 58:4

The deaf adder. The adder, or asp, is the haje naja, or cobra of Egypt, according to Cuvier. The hearing of all the serpent tribes is imperfect, as all are destitute of a tympanic cavity, and of external openings to the ear. The deaf adder is not a particular species. The point of the rebuke is, the pathen, or "adder, "here in question, could hear in some degree but would not; just as the unrighteous judges, or persecutors, of David could hear with their outward ears such appeals as he makes in Ps 58:1-2, but would not. The charmer usually could charm the serpent by shrill sounds, either of his voice or of the flute, the serpent's comparative deafness rendering it the more amenable to those sounds which it could hear. But exceptional cases occurred of a deaf adder which was deaf only in the sense that it refused to hear, or to be acted on. Also Jer 8:17; compare Ec 10:11. A. R. Fausset.