Charles Ellicott Commentary Psalms 58:4

"Their poison is like the poison of a serpent: [They are] like the deaf adder that stoppeth her ear," — Psalms 58:4 (ASV)

Their poison ... —Better, they have a venom like, etc. The term for serpent is the generic nâchash.

The most powerful images of determined wickedness, and of the destruction it brings about, now follow. The first is supplied by the serpent, an image made more suggestive by the accumulated evil qualities for which that animal has been considered the type from the beginning. Here the figure is heightened, as the animal is supposed to have been initially tamed, but suddenly darts out its fangs, revealing itself not only untamed but untamable.

Adder. —Hebrew, pethen, translated as asp in Deuteronomy 32:33, Job 20:14, and Isaiah 11:8 (and here by the Septuagint). In the Bible Educator iv. 103, the pethen is identified with the Egyptian cobra, the species upon which serpent charmers practise their specialized skill.

Deaf. —Similarly, Jeremiah 8:17 refers to various kinds of serpents that will not be charmed. Here, however, it seems as if the poet were thinking of some individual of a species, generally docile, that obstinately resists the spells and incantations of the charmer.

The image of the deaf adder was a favourite with Shakespeare, who, no doubt, derived it from this psalm.

“Pleasure and revenge
Have ears more deaf than adders to the voice
Of any true decision.”

Troilus and Cressida, iii. 2.

(Compare 2 Henry VI, iii. 2.)