Sefer HaChinuch ספר החינוך

To not do an act of ov: To not do an act of ov — and that we not turn to it; meaning to say, that we not ask of it, as it is stated (Leviticus 19:31), “Do not turn to the ovs.” And the content is that they offer well-known incense and perform well-known acts; and through these things, it appears to a person that he hears speech from under the armpit that answers what he will ask. And this is one of its types. And the language of Sifra, Kedoshim, Chapter 7:10 [is] “Ov is pitom which speaks from his armpit.”

That which we have written on the prohibition of the diviner and the soothsayer (Sefer HaChinukh 249, 250) is from the roots of this commandment. And [it is] since all of these nullities cause a person to leave the true fundamental religion and faith in God, may He be blessed; and to turn to emptiness and think that everything that happens to him, happens by way of circumstance; and that it is in his hand to better himself and remove all injury from him with those questions and nullities that he will do. And all of this is not worth it for him, since everything is decreed by the Master of the World. And according to the proper deed or the sin that a person does, do things occur to him — whether good or whether bad — and as it is written (Job 34:11), “For the action of a man does He pay to him.” And upon this it is fitting for a person to order all of his thoughts and to prepare all of his ways. And this is the thought of every person of the good Children of Israel. And also, as there is a tinge of idolatry in this matter of ov and yida’aoni. The details of the commandment are in the seventh chapter of Sanhedrin. (See Mishneh Torah, Laws of Foreign Worship and Customs of the Nations 6.)

And [it] is practiced in every place and at all times by males and females. And one who transgresses it and does [an act of] the ov volitionally and [in view of] witnesses is stoned. And if there are no witnesses [or] warning, it is with excision; [and if done] inadvertently, he brings a fixed sin-offering. And one who inquires of them [only violates] a negative commandment; but if he plans his actions and does according to their words, he is lashed.