183. Spells and Incantations
Avodas Kochavim 11:10
An enchanter is one who utters incantations that have no meaning and he imagines that his nonsense has an effect. They will say that you can cast a spell on a snake or a scorpion to prevent it from causing harm, or on a person to make him impervious to harm. Some of them hold a key or a rock while casting their spells, or perform other actions. All of these are prohibited.
One who casts spells is liable to the penalty of lashes if he holds something in his hand or performs an action while he is speaking. This includes simply gesturing with his finger. Deuteronomy 18:10-11 says, “There shall not be found among you... one who casts spells.” If, however, he merely spoke without gesturing or holding anything, he is liable to stripes for being rebellious. The same is true of one who had a spell cast over him thinking that it would help him in some way. Incantations and spells do nothing – they can neither harm nor help.
Avodas Kochavim 11:11
If a person is bitten by a scorpion or a snake, it is permitted to utter incantations over the bite, even on Shabbos, in order to calm the person and strengthen him. Even though such incantations can do nothing, permission was granted in such a case in order to keep the victim from panicking and further endangering his life.