Sefer HaChinuch ספר החינוך

To not divine: That we not follow divinations, as it is stated (Leviticus 19:26), “you shall not divine.” And it is repeated in another place, as it is stated (Deuteronomy 18:10), “There shall not be found in you, etc. or a diviner.” And they said in Sifrei Devarim (Shoftim), “‘A diviner’ — such as one who says, ‘My bread fell from my mouth, the stick fell from my hand, a snake passed on my right and a fox on my left,’ and he refrains from some act because of it.” And in Sifra, Kedoshim, Chapter 6:2 they said, “‘You shall not divine’ - such as those that divine with weasels, birds, stars and what is similar to them.” To here [are the words of the Sifra]. And such as that which the silly masses among the nations say: Since he came back from his path that he was walking, a deer passed in front of him, or a yelling crow passed over his head or if he saw thing x at the beginning of the day — he will not have profit today or any [other] bad event will come to him. And all of these acts and similar to them are included in this negative commandment.

It is from the roots of the commandment [that it is] because these matters are crazy things and total foolishness; and it is not fitting for the holy true people that God chose that they pay attention to false words. And also because they are a cause to push man away from faith in God, may He be blessed, and from His holy Torah and to come through them to complete denial [of God and/or Torah]; as he will think that all of his good and all of his evil and all that happens to him is coincidental, and not from the supervision of his Creator. And it will happen that through this he will go out from all of the principles of the religion. Therefore, since God, may He be blessed, wanted our good, He commanded us to remove this thought from our hearts. As all the bad and the good comes out of the mouth of the Most High, according to the actions of man — if they are good, or if they are evil. And the divinations do not [help or hurt], and as it is written (Numbers 23:23), “As there is no divination in Yaakov and no clairvoyance in Israel.” The details of the commandment are in the seventh chapter of Shabbat [in Chapter 6 of Sanhedrin] and in the Tosefta Shabbat, Chapter 8.

And [it] is practiced in every place and at all times by males and females. And one who transgresses it and does any act according to divination with witnesses and a warning is lashed — and specifically with a court of twenty-three. In every place that we wrote “lashed,” in that which preceded and that which we will write, the intention is in the Holy Land — since it is the place of the judgment of twenty-three. As we do not judge capital cases outside of the Land, except only with a talebearer; since his death is the salvation and resuscitation of others better than he.