def (cheresh; kophos): Used either in the physical sense, or figuratively as expressing unwillingness to hear the Divine message (Ps 58:4), or incapacity to understand it for want of spirituality (Ps 38:13). The prophetic utterances were sufficiently forcible to compel even such to hear (Isa 42:18; 43:8) and thereby to receive the Divine mercy (Isa 29:18; 35:5).
The expression "deaf adder that stoppeth her car" (Ps 58:4) alludes to a curious notion that the adder, to avoid hearing the voice of the charmer, laid its head with one car on the ground and stopped the other with the tip of its tail (Diary of John Manninghan, 1602). The adder is called deaf by Shakespeare (2 Hen VI, iii, 2, 76; Troilus and Cressida, ii, 2, 172). The erroneous idea probably arose from the absence of external ears.
Physical deafness was regarded as a judgment from God (Ex 4:11; Mic 7:16), and it was consequently impious to curse the deaf (Le 19:14). In New Testament times deafness and kindred defects were attributed to evil spirits (Mr 9:18 ff).