Why does the Torah juxtapose the Parshah of Mechashef to that of Mefateh?
Oznayim la'Torah: Because if a man fancies a certain woman, he sometimes turns to a witch to cast a spell on her that she will agree to marry him.
What is the definition of "Mechashef"?
A sorceress is Chayav Sekilah (Sanhedrin, 53b). Why does the Torah place a La'av against allowing her to live, rather than an Asei to sentence her to death,, as it does by other Chayvei Misah (See Shoftim, Devarim 17:7 and above, 21:12?
Ramban: Because of the deep Tum'ah that is inherent in sorcery, which, due to powerful attraction that it holds over the fools who cleave to it, wreaks havoc among the people. 1
Rashbam: Because it is the way of sorceresses to ply their trade in secret, and one needs to make a great effort to find and eliminate them. 2
Hadar Zekenim: Because if the Sanhedrin would execute her, perhaps she would save herself through witchcraft. Therefore, anyone who can kill a witch is rewarded. 3
Ramban: And the Torah tends to treat more stringently sins that causes others to stumble or that threaten them - such as a Meisis (See Devarim 13:9) and a murderer (See Bamidbar 35:31).
Rashbam: Such as the episode with the eighty witches of Ashkelon whom Shimon ben Shetach hanged (See Yerushalmi Sanhedrin 6:6).
Hadar Zekenim: Which explains why Shimon ben Shetach hung eighty witches (not through the Sanhedrin) - Yerushalmi Sanhedrin 6:6.
To which form of death is a Mechashef sentenced?
Targum Yonasan and Sanhedrin, 67a: Sekilah (based on the Gezeirah Shavah "Lo Sechayeh" "Lo Yichyeh" in Yisro Sh'mos, 19:13 in connection with Har Sinai - Sanhedrin).
Why does the Torah refer to a sorceress and not a sorcerer?
Rashi and Ramban (in Parshas Shoftim, 17:2) 1 : Because sorcery is more common among women than among men. 2