BLASPHEMY, in the broadest (and least precise) sense any act contrary to the will of God or derogatory to His power. Blasphemy is the term employed to translate the Hebrew verbs ḥeref, giddef, and ni'eẓ (e.g., Isa. 37:6, gdf, where the servants of the king of Assyria denied the Lord's power to save Israel; and Ezek. 20:27, where it refers to Israel's sacrifices on the High Places). In the narrower and more precise sense, the word is used to mean speaking contemptuously of the Deity. The classic instance in the Bible is Leviticus 24:10–23, where the pronouncement (nakav, naqav) of the name of God appears in conjunction with the verb killel (qillel). God (Elohim) also appears as the object of the verb qillel in Exodus 22:27 (see also I Kings 21:10, 13, where qillel is euphemistically displaced by its antonym berekh, "to bless" or "to renounce"; see *Euphemism and Dysphemism). The rabbinic interpretation of Leviticus 24:10–23 and Exodus 22:27 as wishing (i.e., wishing harm, Sanh. 7:5) establishes a definition of blasphemy such as to render the actual perpetration (and the application of the penalty, capital punishment) out of the realm of probability. The verb qallel rarely means "to curse." Rather it subsumes a wide range of abuse, often nonverbal in nature. "To curse" the Deity meant to repudiate Him, to violate His norms; blasphemy on the part of an Israelite, in the narrow sense, is a concept alien to biblical thought.
Eisenstein, Dinim, 68.