Halakhah sa Oseas 4:12: Mishneh Torah, Foreign Worship and Customs & Sefer HaChinukh

Who is practitioner of divination? He who occupies himself with purposeless actions so as to divert his thoughts from all relevancy, thereby preparing himself to prognosticate, and, then, foretells, saying: "That thing will come to pass," or, "it will not come to pass", or he will say: "It is proper to do so, but beware from doing otherwise." There are some soothsayers who use sand or stones as a medium, and there others who spread themselves out on the ground and fall in convulsions and cry out; there are some who look into an iron mirror or goblet and imagine things and say them, and there are others who carry a cane in hand upon which to lean, wherewith a process of knocking is continued as a diversion until the mind is ready, then the speaking starts. Upon such the prophet proclaims, saying: "My people ask counsel at their stock, and their staff declareth unto them" (Hosea, 4. 12).⁹Sanhedrin, 65b; Sifre, Deut. 18. G.

And I have already written in the warning (negative commandment) about “do not divine” in the Order of Kedoshim (Sefer HaChinukh 249) what I have known about the reason for these matters. And I saw in the books of the early scholars about the reason for this prohibition, [that it is] because all of these matters mislead the masses. And because some of what the clairvoyants tell them come out to be true, they think that the constellations and powers are the cause of all actions that are in the world. And they can almost be called part of the evil group that say, “The Lord has abandoned the land” (Ezekiel 8:12). And because of this matter which was very famous at the time of the prophets, the prophet said, “My people asks its wood, and its stick will speak to it” (Hoshea 4:12).