Psalms 58:4

Their poison [is] like the poison of a serpent: [they are] like the deaf adder [that] stoppeth her ear;

Ver. 4. Their poison is like the poison of a serpent] Their inbred corruption (the spawn of that old serpent, Gen 3:1-14) is strong, and full of infection, able to kill both the party in whom it is and the other also upon whom it is cast. Malice drinketh up the most part of its own venom, but some it spitteth out upon others; for it is not like the maid whom Avicen mentioneth, who, feeding upon poison, was herself healthy, yet infected others with her venomous breath, Deuteronomy 32:33. Hot poison have they, like as the hot poison of a serpent (so some render it), yea, of the worst sort of serpents, the asp (for serpentum quot colores tot dolores, saith Isidore), the venom whereof is incurable, saith Pliny, lib. viii. c. 3; unless the members touched therewith be immediately cut off.

They are like the deaf adder (or asp) that stoppeth her ear] So that their naughtiness is not natural only, but habitual, acquired, wilful; they refuse to be reformed, they hate to be healed, and must, therefore, be turned over to God with a Noluerunt incantari, they would not be reclaimed, they are uncounselable, unpersuasible. The adder or asp here hath her name Pethen, from persuasibleness, but it is by antiphrasis. Wicked men are likewise said to be απειθεις, unpersuaded, or disobedient, Titus 1:16, and children of disobedience, Ephesians 2:2, such as whom Non persuadebis etiamsi persuaseris, speak you never so persuasively, ye shall never persuade. Nay, but we will have a king, said they of old, when they had nothing else to say. So Pharaoh, when clearly convinced, sent for the sorcerers.