What are the implications of "Lo Silmad La'asos ... "?
Rashi: It implies that one may not learn from the Cana'anim in order to put their ways into practice, but one may learn in order to understand and to teach 1 .
Rashi: To understand how evil their practices are and to instruct one's children not to emulate them. See also Torah Temimah, note 57.
Having already taught in Acharei-Mos Vayikra, 18:3 "ke'Ma'aseh Eretz Cana'an ... Lo Sa'asu", why does the Torah repeat it here?
Ramban: Because there the Torah spoke only in general terms, whereas here it describes what those wicked deeds are.
Why does the Torah not insert 'ke'Ma'aseh Eretz Mitzrayim", like it did in Acharei-Mos?
Oznayim la'Torah #1: Because Moshe is speaking here to the new generation, who had long forgotten - who never even saw - the witchcraft of the Egyptians. 1
Oznayim la'Torah #2 (based on the Ha'amek Davar, who explains that the main purpose of the witchcraft practiced in Cana'an was in order discover when the rain would fall, so that they could synchronize planting their crops with the rainfall. Consequently, it was necessary to warn Yisrael not to emulate the Cana'anim when they entered the land - which also explains why the Torah sees fit to repeat the warning against witchcraft here.
See Oznayim la'Torah.
