Ramban on Deuteronomy 4:2

לֹא תוֹסִיפוּ, כְּגוֹן חָמֵשׁ פָּרָשִׁיּוֹת בַּתְּפִלִּין חֲמִשָּׁה מִינִין בַּלּוּלָב חָמֵשׁ צִיצִיּוֹת, וְכֵן לֹא תִגְרְעוּ, לְשׁוֹן רַשִׁ"י (רש"י על דברים ד':ב'). וְכָךְ אָמְרוּ בְּסִפְרֵי (ראה), מִנַּיִן שֶׁלֹּא תּוֹסִיף עַל הַלּוּלָב וְעַל הַצִּיצִית, ת"ל לֹא תוֹסִיפוּ. וּמִנַּיִן שֶׁאֵין פּוֹחֲתִים מֵהֶן, ת"ל לֹא תִגְרְעוּ. מִנַּיִן שֶׁאִם פָּתַח לְבָרֵךְ בִּרְכַּת כֹּהֲנִים לֹא יֹאמַר הוֹאִיל וּפָתַחְתִּי לְבָרֵךְ אוֹמַר ה' אֱלֹהֵי אֲבוֹתֵיכֶם יוֹסֵף עֲלֵיכֶם, ת"ל הַדָּבָר, אֲפִלּוּ דָּבָר לֹא תּוֹסֵף עָלָיו. אֲבָל לֹא בְּאֵלֶּה בִּלְבַד אָמְרוּ, אֶלָּא אַף הַיָּשֵׁן בַּסֻּכָּה בַּשְּׁמִינִי בְּכַוָּנָה לוֹקֶה, כְּמוֹ שֶׁמֻּזְכָּר בְּמַסֶּכֶת רֹאשׁ הַשָּׁנָה (ראש השנה כ"ח). וְכֵן אִם יַעֲשֶׂה הֶחָג שִׁשָּׁה, עוֹבֵר בַּלָּאו הַזֶּה. וּלְפִי דַּעְתִּי אֲפִלּוּ בָּדָא לַעֲשׂוֹת מִצְוָה בִּפְנֵי עַצְמָהּ, כְּגוֹן שֶׁעָשָׂה חַג בַּחֹדֶשׁ שֶׁבָּדָא מִלִּבּוֹ כְּיָרָבְעָם (מלכים א יב לג), עוֹבֵר בְּלָאו. וְכָךְ אָמְרוּ (מגילה יד) לְעִנְיַן מִקְרָא מְגִלָּה, מֵאָה וּשְׁמוֹנִים נְבִיאִים עָמְדוּ לָהֶם לְיִשְׂרָאֵל וְלֹא פִּחֲתוּ וְלֹא הוֹסִיפוּ עַל מָה שֶׁכָּתוּב בַּתּוֹרָה אֲפִלּוּ אוֹת אַחַת חוּץ מִמִּקְרָא מְגִלָּה, מַאי דְּרוּשׁ וְכוּ'. וּבַיְּרוּשַׁלְמִי (מגילה פ"א ה"ז) שְׁמוֹנִים וַחֲמִשָּׁה זְקֵנִים וּמֵהֶם כַּמָּה נְבִיאִים הָיוּ מִצְטַעֲרִים עַל הַדָּבָר, אָמְרוּ כָּתוּב אֵלֶּה הַמִּצְוֹת אֲשֶׁר צִוָּה ה' אֶת מֹשֶׁה, אֵלּוּ הַמִּצְוֹת שֶׁנִּצְטַוּוּ מִפִּי מֹשֶׁה, כָּךְ אָמַר לָנוּ מֹשֶׁה וְאֵין נָבִיא אַחֵר עָתִיד לְחַדֵּשׁ דָּבָר לָכֶם, וּמָרְדְּכַי וְאֶסְתֵּר רוֹצִים לְחַדֵּשׁ לָנוּ דָּבָר. לֹא זָזוּ מִשָּׁם נוֹשְׂאִין וְנוֹתְנִין בַּדָּבָר עַד שֶׁהֵאִיר הקב"ה עֵינֵיהֶם וְכוּ'. הֲרֵי שֶׁהָיְתָה הַמִּצְוָה הַזּוֹ אֲסוּרָה לָהֶם, א"כ הִיא בִּכְלַל לֹא תֹסֵף עָלָיו. אֶלָּא שֶׁלֹּא לָמַדְנוּ לְמוֹסִיף עַל פִּי נָבִיא אֶלָּא מִן הַכָּתוּב שֶׁאָמַר אֵלֶּה הַמִּצְוֹת, אֵין נָבִיא רַשַּׁאי לְחַדֵּשׁ בּוֹ דָּבָר מֵעַתָּה. וּמָה שֶׁתִּקְּנוּ חֲכָמִים מִשּׁוּם גָּדֵר, כְּגוֹן שְׁנִיּוֹת לָעֲרָיוֹת וְכַיּוֹצֵא בָּהֶן, זוֹ הִיא מִצְוָה מִן הַתּוֹרָה, וּבִלְבַד שֶׁיֵּדַע שֶׁהֵם מִשּׁוּם הַגָּדֵר הַזֶּה וְאֵינָן מִפִּי הקב"ה בַּתּוֹרָה: YE SHALL NOT ADD [UNTO THE WORD WHICH I COMMAND YOU] — “such as placing five sections [of the Torah] in the phylacteries, five species in a lulav,²²The four species in the commandment of the lulav are: the palm-branch, the ethrog, the myrtle and the willows. — For phylacteries See Vol. II, p. 168, Note 406. five fringes [in a garment].²³Further 22:12. The same principle applies to the prohibition, neither shall ye diminish from it” [by placing three sections of the Torah in the phylacteries etc.]. This is Rashi’s language. And thus the Rabbis said in the Sifre:²⁴Sifre, R’eih 82. “Whence do we know that you are not to add to [the four species in the commandment of] the lulav,²²The four species in the commandment of the lulav are: the palm-branch, the ethrog, the myrtle and the willows. — For phylacteries See Vol. II, p. 168, Note 406. nor to the [four] fringes?²³Further 22:12. Scripture therefore says, Ye shall not add. And whence do we know that you are not to diminish from them? Because Scripture states, neither shall ye diminish. Whence do we know that if [a priest] began to recite the Priestly Blessing²⁵Numbers 6:24-26. he is not to say: ‘Since I began to bless [the people], I will [further] say, The Eternal, the G-d of your fathers, make you a thousand times so many more as ye are?’²⁶Above, 1:11. Because Scripture states, [Ye shall not add] unto the ‘word’ — even ‘a word’ you are not to add to it.” However, not only concerning these [commandments] have the Rabbis said [that the prohibitions neither to add nor to diminish, apply], but also in the case of someone who sleeps in a Booth on the eighth Day [of the Festival of Tabernacles]²⁷Leviticus 23:42: Ye shall dwell in Booths ‘seven’ days. Thus the Torah specifically states that the commandment to dwell in Booths applies to seven days only, and not to the eighth Day, which is a separate festival (Shemini Atzereth). Sleeping is part of the commandment “to dwell” in a Booth. [However, because of the general rule that he who feels uncomfortable is exempt from sitting in a Booth, sleeping there, in the colder climates in which we live, is practiced only by those who are very strict in religious observance (Orach Chayim 639:2, R’ma).] with the intent [of performing a religious duty] that he is liable to whipping [for having added to the commandment], as is mentioned in Tractate Rosh Hashanah.²⁸Rosh Hashanah 28 b. So also if he were to observe the Festival of Tabernacles for only six days, he would be transgressing this negative commandment [neither shall ye diminish from it].
In my opinion, even if someone devised an independent commandment [rather than altering an existing one] such as establishing a festival in a month which he had devised of his own accord,²⁹I Kings 12:33. as Jeroboam did,²⁹I Kings 12:33. he transgresses the negative commandment [Ye shall not add unto the word which I command you]. And so did the Rabbis say with reference to the reading of the Scroll of Esther [on Purim]:³⁰Megillah 14 a. “One hundred and eighty prophets³¹In our text of the Talmud: “Forty-eight prophets.” See my Hebrew commentary, page 360. arose in Israel and they did not diminish from nor add even one letter to what was written in the Torah, except for reading the Scroll of Esther [which was instituted by the prophets]. What basis did they have for that? etc.”³²“Rabbi Chiya bar Abbin in the name of Rabbi Yehoshua ben Korcha said: It is a matter of kal vachomer (reasoning from minor to major): If [when Israel was delivered] from slavery to freedom they sang [in praise of G-d], how much more ought they to do so when they were saved from death [that was decreed upon Israel through the plot of Haman] to life!” (Megillah 14 b). The reading of the Scroll of Esther constitutes the praise to G-d for our deliverance (ibid.). And in the Yerushalmi it is stated:³³Yerushalmi Megillah I, 7. On the term “Yerushalmi” see Vol. III, p. 192, Note 44. “Eighty-five elders, among them many prophets, were troubled about the matter [of the new duty to read the Scroll of Esther]. They said, ‘It is written, These are the commandments which the Eternal commanded Moses.³⁴Leviticus 27:34. These are the commandments that [we] were ordered by the mouth of Moses, and Moses told us that no other prophet is destined to establish anything new for you — and Mordecai and Esther want to establish something new for us!’ They did not move from there while discussing the matter, until the Holy One, blessed be He, enlightened their eyes [and they found the new commandment intimated in the Torah, Prophets, and Writings].” Thus you see that [the institution of] this commandment [of reading the Scroll of Esther on Purim] would have been forbidden to them [were it not for the fact that ultimately they found it intimated in the Torah, etc.]; otherwise it would have been included in the principle, thou shalt not add thereto.³⁵Further, 13:1. — It should be noted that at this point Ramban cites the later verse (13:1) instead of the verse here. The reason would seem to be that the verse here relates to adding to, or diminishing from, a Divine commandment, such as placing five sections of the Torah, or only three, in the phylacteries instead of the four sections ordained. The verse of 13:1, however, refers to adding a completely new commandment to the number of Taryag (613) Commandments, or of abolishing altogether one of the Divine precepts. In speaking, therefore, of the prophetic precept of reading the Scroll of Esther on Purim, Ramban thus rightly cites the verse from further on (13:1), for were it not that the prophets and Sages of that time found it intimated in the Torah, the prohibition against instituting such a new commandment would have come under the admonition, thou shalt not add thereto. However, the prohibition against adding [to the Torah] by word of a prophet we derive only from the verse stating, These are the commandments,³⁴Leviticus 27:34. which establishes,³⁶Torath Kohanim, at end of Bechukothai. “From now on, no prophet is permitted to originate anything [in the Torah].” Whatever [laws] the Sages have established in the nature of “a fence [around the Torah],” such as the secondary degrees of forbidden marriages³⁷Yebamoth 21a-b. — that activity of [establishing fences] is itself a requirement of the Torah, provided only that one realizes that these [laws] are a result of a particular fence and that they are not [expressly] from the mouth of the Holy One, blessed be He, in the Torah.³⁸In other words, the duty devolving upon the Sages to establish “fences” [i.e., safeguards against trespassing the law of the Torah] is specifically stated in the Torah, but the precise terms of these “fences” are not written. — The duty of establishing such preventive Rabbinical laws is based on the verse, ushmartem eth mishmarti (and ye shall keep My charge — Leviticus 18:30), tradition interpreting this to mean: “Make a mishmereth (a protection, a fence as a safeguard) l’mishmarti (for My commandment)” (Yebamoth 21 b).