Sefer HaChinuch ספר החינוך

To not do an act of yida’aoni: To not do an act of yida’aoni, as it is stated (Leviticus 19:31), “Do not turn to the ovs and to the yida’aonis.” And Rambam, may his memory be blessed, explained (Sefer HaMitzvot, Negative Commandments 9) and this is his language: “That the matter is that he takes a bone of a bird the name of which is yido’a, places it into his mouth, burns types of incense to it, makes incantations and performs actions, until he is connected with the matter of the disease of epilepsy — like the disease that is called sovat — and speaks out predictions. And so did they, may their memory be blessed, say (Sanhedrin 65a), ‘Yida’aoni [is that] he places a well-known bone into his mouth and it speaks on its own.’ And do not think that this is a general negative commandment, as it already separated them: When it mentioned the punishment, it stated, ‘ov or a yida’aoni’ and made one liable for stoning and excision for each of the two of them, when volitional. And that is its stating (Leviticus 10:1), ‘And a man or a woman that has an ov or a yida’aoni with them shall surely be killed, etc.’ And the language of Sifra, Kedoshim, Chapter 9:1 [is]: ‘Since it states, “And a man or a woman, etc.” We have heard the punishment; from where [do I know] the warning? [Hence] we learn to say, “Do not turn to the ovs and to the yida’aonis.”’” Its neighbor, ov (Sefer HaChinukh 255), will speak about all of the content of yida’aoni. And there in Sanhedrin [in] the sixth chapter are its laws also elucidated.