ג וְכָל הַלָּאוִין הָאֵלּוּ בְּעִנְיָן אֶחָד הֵן וְהוּא שֶׁלֹּא יִפְנֶה אַחַר עֲבוֹדַת כּוֹכָבִים וְכָל הַנִּפְנֶה אַחֲרֶיהָ בְּדֶרֶךְ שֶׁהוּא עוֹשֶׂה בּוֹ מַעֲשֶׂה הֲרֵי זֶה לוֹקֶה. וְלֹא עֲבוֹדַת כּוֹכָבִים בִּלְבַד הוּא שֶׁאָסוּר לְהִפָּנוֹת אַחֲרֶיהָ בְּמַחֲשָׁבָה אֶלָּא כָּל מַחֲשָׁבָה שֶׁהוּא גּוֹרֵם לוֹ לָאָדָם לַעֲקֹר עִקָּר מֵעִקְּרֵי הַתּוֹרָה מֻזְהָרִין אָנוּ שֶׁלֹּא לְהַעֲלוֹתָהּ עַל לִבֵּנוּ וְלֹא נַסִּיחַ דַּעְתֵּנוּ לְכָךְ וְנַחְשֹׁב וְנִמָּשֵׁךְ אַחַר הִרְהוּרֵי הַלֵּב. מִפְּנֵי שֶׁדַּעְתּוֹ שֶׁל אָדָם קְצָרָה וְלֹא כָּל הַדֵּעוֹת יְכוֹלִין לְהַשִּׂיג הָאֱמֶת עַל בֻּרְיוֹ. וְאִם יִמָּשֵׁךְ כָּל אָדָם אַחַר מַחְשְׁבוֹת לִבּוֹ נִמְצָא מַחֲרִיב אֶת הָעוֹלָם לְפִי קֹצֶר דַּעְתּוֹ. כֵּיצַד. פְּעָמִים יָתוּר אַחַר עֲבוֹדַת כּוֹכָבִים וּפְעָמִים יַחְשֹׁב בְּיִחוּד הַבּוֹרֵא שֶׁמָּא הוּא שֶׁמָּא אֵינוֹ. מַה לְּמַעְלָה וּמַה לְּמַטָּה מַה לְּפָנִים וּמַה לְּאָחוֹר. וּפְעָמִים בַּנְּבוּאָה שֶׁמָּא הִיא אֱמֶת שֶׁמָּא הִיא אֵינָהּ. וּפְעָמִים בַּתּוֹרָה שֶׁמָּא הִיא מִן הַשָּׁמַיִם שֶׁמָּא אֵינָהּ. וְאֵינוֹ יוֹדֵעַ הַמִּדּוֹת שֶׁיָּדִין בָּהֶן עַד שֶׁיֵּדַע הָאֱמֶת עַל בֻּרְיוֹ וְנִמְצָא יוֹצֵא לִידֵי מִינוּת. וְעַל עִנְיָן זֶה הִזְהִירָה תּוֹרָה וְנֶאֱמַר בָּהּ (במדבר טו לט) "וְלֹא תָתֻרוּ אַחֲרֵי לְבַבְכֶם וְאַחֲרֵי עֵינֵיכֶם אֲשֶׁר אַתֶּם זֹנִים". כְּלוֹמַר לֹא יִמָּשֵׁךְ כָּל אֶחָד מִכֶּם אַחַר דַּעְתּוֹ הַקְּצָרָה וִידַמֶּה שֶׁמַּחֲשַׁבְתּוֹ מַשֶּׂגֶת הָאֱמֶת. כָּךְ אָמְרוּ חֲכָמִים (גמרא ברכות יב ב) "אַחֲרֵי לְבַבְכֶם זוֹ מִינוּת" וְאַחֲרֵי עֵינֵיכֶם זוֹ זְנוּת. וְלָאו זֶה אַף עַל פִּי שֶׁהוּא גּוֹרֵם לָאָדָם לְטָרְדוֹ מִן הָעוֹלָם הַבָּא אֵין בּוֹ מַלְקוֹת:
3 All of these prohibitive commandments are concentrated on one subject, namely: Not to turn after idolatry, and whosoever does turn after it by doing aught resembling its practice is guilty of an offense punishable by lashes. And, yet, not turning after idolatry alone in one's thoughts is forbidden, for even concerning all thought which causes man to delete a principle of the fundamentals of the Torah are we charged not to offer it to our heart, not to concentrate our mind thereon and reason it out and be drawn after the swerving fancies of the heart. Preceding all, behold, the short-coming of man's intelligence, more particularly that not all minds can attain the purity of truth. Now, if every man be drawn away after his heart's fancies, he will be discovered demolishing the world to fit in the shortsightedness of his intelligence. For example: some of the time he will search after idolatry, and some of the time he will meditate about the Unity of the Creator, perhaps He is, and perhaps He is not, what of above and what of below, what of the beginning and what of the end; some of the time he will meditate concerning prophecy, perhaps there is, and perhaps there is not, and some of the time about the Torah, perhaps it is from heaven and perhaps it is not. Whereas, he knows not the standard of thinking wherewith to discover the knowledge of pure truth, as a consequence whereof he goes without to atheism. Even on, this subject there is a warning in the Torah, for it says therein: "And that ye go not about after your own heart and your own eyes, after which ye use to go astray" (Num. 15. 39.), as if saying: "Let not any of you be drawn after his short-sighted intelligence and imagine that his fancy attains the truth". Thus did the wise men say: "After your own heart", is a warning against atheism; and "After your own eyes", is a warning against prostitution (Berakot, 13a). But the violation of this prohibitive commandment, although it causes man's disability to share in the World to Come, is not punishable by lashes.