Siman 410

(4.) And once on Rosh Hashana Rabbainu o.b.m. also spoke about this — about the immensity of the prohibition to study these books that explain the Torah according to the ways of the philosophers — such as the books of Ibn Ezra, and particularly the bad commentary on him called Margalis Ra'ah; and the books of the Ralbag, which are well known to all for what is written there against the holy Torah — for which a person is obligated to tear his garments when hearing G-d forbid even one such word. And so on and so forth... And so on and so forth — whose introductions all took from Aristotle the Greek, may his name be blotted out and his memory erased, and the other publicized heretics — some of whom were before the Sages of the Talmud and some in their days. For the whole intention of the holy authors of the Mishnah and Gemara who forbade studying books of Greek wisdom was upon these books of those heretics, all of which were then among the Greeks. And wherever our Sages of blessed memory mention an epikoros, their intention is toward one who is drawn after their ways and notions. Therefore other complete resha'im who have any heresy whatsoever are also called epikorsim, for they hang the corruption on the corrupter. For there was a philosopher whose name was Apikores [Epikoros] — as is his name so is he, may his name and memory be blotted out — and his bad view is publicized in their bad books. And how can it enter the mind of one who wants to be a Jew to look into books like these, built on the bad foundations of publicized heretics, from whom are drawn all the heretics and deniers in the world. And it is impossible to explain in writing all that Rabbainu o.b.m. spoke of this immense prohibition to study in these books, G-d forbid. And then Rabbainu o.b.m. spoke with us, and said that one should study books of drush and mussar only those that follow the words of our Sages of blessed memory — in the Gemara and Midrashim, and the holy Zohar, and the books of the Ariza.l o.b.m. — and likewise all the books that the tzaddikim close to our generations composed, which are built upon the mountains of holiness according to the words of the Baal Shem Tov o.b.m. These are the books of the holy rav of Polnoa, and the book Likutey Amorim. And he counted several more such books that are good to study. And the discerning one will understand on his own, according to these words, from which books to keep far, and in which books to strengthen and to grasp — that is, those built only upon the Gemara and Midrashim, and the holy Zohar, and the Ariza.l o.b.m., and the Baal Shem Tov o.b.m. Fortunate is he who grasps them: