He prohibited us from inquiring of the dead - as is thought by those that are truly dead, even though they eat and feel - and think that one who does such and dresses like this will have a dead person come to him during [his] sleep and tell him what he asks. And that is His, may He be exalted, saying, "Let no one be found among you, etc. or one who inquires of the dead" (Deuteronomy 18:10-11). And in the Gemara, Sanhedrin (Sanhedrin 65b), [it says,] "'One who inquires of the dead' - this is one who starves himself and lodges in a graveyard so that a spirit of impurity should settle upon him." And anyone who violates this negative commandment is liable for lashes. (See Parashat Shoftim; Mishneh Torah, Foreign Worship and Customs of the Nations 11.)