EXOD733 Do not curse God. Hashem separated man from the animals by bestowing upon him the power of speech. He gave man this power as a gift, for man’s good, to lift mankind above the animals. However, if a person curses Hashem he uses this gift for evil and thereby falls lower than the most disgusting vermin. His act is totally mindless. Therefore, the Torah warns us about the matter, for Hashem wants to send us only good, and any manner of speech that prevents Him from sending good to us is against His Will.