Halakhah for Shabbat 133:14

The laws of the commandment are in scattered places in the Talmud, but mainly in the seventh chapter of Sanhedrin. And anyone who is a judge about it needs to know the wisdom of magic so that he will be able to distinguish about an act that is done, whether it is one of the types of magic or perhaps from the things done through the power of nature and in permissible ways. And [it is] like the matter that they, may their memory be blessed, said (Shabbat 67a), "Anything that contains [an element] of healing does not contain [the prohibition] on account of the ways of the Amorite." And I have already spoken according to my ability about this, there on the negative commandment of "Do not keep alive a witch." And these matters require great analysis - as behold, acts are found in the Gemara that if we did not know them from their mouth, may their memory be blessed, we would have forbidden them from a concern about this prohibition. But behold nonetheless, one who raises his soul to enter into these machinations - and compares one thing to another from those things that they, may their memory be blessed, mentioned [as being permissible] - is like one who opens an opening to go to Gehinnom.