Mishneh Torah, Negative Mitzvot 1-365

Sugya Map

The Dialectic of Divine and Rabbinic Authority

The concluding paragraphs of the Rambam's enumeration of the 365 Negative Mitzvot pivot dramatically from a granular list of prohibitions to a meta-halachic exposition concerning the fundamental nature of Mitzvot DeRabanan (Rabbinic commandments) and their legitimacy within the Torah framework. The core issue wrestled with here is the apparent tension between the Torah's stringent prohibition of Bal Tosif u'Val Tigra ("Do not add to it and do not diminish from it")¹ and the undisputed authority of the Sages to institute new mitzvot or decrees. How can Chazal (our Sages, of blessed memory) "add" observances like Chanukah or Purim without transgressing a direct Torah command?

Nafka Mina(s) (Practical and Conceptual Implications)

This sugya is not merely academic; its ramifications are profound, touching upon:

• The Binding Force of Rabbinic Law: It delineates the source and scope of the obligation to observe Mitzvot DeRabanan, whether they are gezeirot (protective fences), takanot (ordinances), or minhagim (customs). Do they derive their authority independently or through a Torah mandate?
• Prophetic Authority Post-Sinai: The Rambam's formulation distinguishes between a prophet claiming new mitzvot from God and a court (even with a prophet) instituting decrees. This clarifies the limits of prophecy in the halachic realm after the giving of the Torah.
• The Nature of Halachic Development: It provides the foundational heuristic for how halacha can evolve and respond to new circumstances while maintaining fidelity to its Sinaitic origins, preventing both stagnation and unwarranted innovation.
• Defining "Mitzvah": It sheds light on why Rabbinic enactments are often referred to as "mitzvot," despite not being explicitly commanded in the Torah.

Primary Sources

• Deuteronomy 13:1 (12:32 in some editions): "Do not add to it and do not diminish from it." (לֹא תֹסֵף עָלָיו וְלֹא תִגְרַע מִמֶּנּוּ). This is the explicit prohibition against Bal Tosif.
• Deuteronomy 17:11: "You shall not deviate from the word that they tell you, right or left." (לֹא תָסוּר מִן הַדָּבָר אֲשֶׁר יַגִּידוּ לְךָ יָמִין וּשְׂמֹאל). This is the source for the obligation of Lo Tasur, to obey the rulings of the Sanhedrin.
• Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section): The immediate text under analysis, where the Rambam articulates his reconciliation.
• Rambam, Sefer HaMitzvot, Shoresh Rishon and Shoresh Sheni: The fundamental methodological roots of his counting and understanding of mitzvot, which directly inform this discussion.
• Rambam, Hilchot Mamrim 1:1-2:2: Provides the comprehensive legal framework for the authority of the Sanhedrin and the prohibition of Bal Tosif.

Text Snapshot

The crux of the Rambam's exposition on Rabbinic authority and Bal Tosif lies in the concluding paragraphs of Mishneh Torah, Negative Mitzvot 1-365. Let's zero in on the exact lines and their subtle nuances:

"These 613 mitzvot were given to Moses on Mount Sinai together with their general principles, particular points, and details. These general principles, particular points, and details represent the Oral Law, which each court received from the previous court."²

"And there are [also] other commandments that were instituted after the giving of the Torah. They were established by the Prophets and Sages and spread throughout Israel, for example, the reading of the Megillah, [lighting] a Chanukah candle, fasting on Tish'ah b'Av, [setting up] eruvim, and [washing one's] hands [in preparation for prayer and eating]. Each of these commandments also possesses explanatory aspects and details."³

"We are obligated to accept and observe all these commandments which [the Rabbis] instituted, as [implied by Deuteronomy 17:11]: 'Do not deviate from the instructions that they will give you, left or right.' They are not considered to be additions to the commandments of the Torah."⁴

"What was the intention of the Torah's warning (Deuteronomy 13:1): 'Do not add to it and do not diminish from it'? That a prophet is not permitted to introduce a new measure and say that the Holy One, blessed be He, commanded this mitzvah to us and that it should be added to the Torah's mitzvot, or [say that He commanded that we] eliminate one of the 613 mitzvot mentioned above."⁵

"However, if a court, together with the prophet of that age, adds a commandment as an ordinance, a lesson, or as a decree, this is not considered as an addition. He is not saying that the Holy One, blessed be He, commanded us to make an eruv or read the Megillah at its [appointed] time. Were he to say so, he would be adding to the Torah."⁶

"Instead, we are saying that the prophets and the courts ordained and commanded that the Megillah be read at its [appointed] time in order to recall the praise of the Holy One, blessed be He, the salvation He wrought for us, and His response to our cries, so that we will bless Him, extol Him, and inform the future generations of the truth of the Torah's promise (Deuteronomy 4:7): 'What nation is so great that it has God [close to it....]'."⁷

"Similar principles apply with regard to all the other Rabbinic commandments, be they positive commandments or negative commandments."⁸

Dikduk/Leshon Nuance

The Rambam employs precise terminology to delineate his position:

• "וְיֵשׁ עוֹד מִצְוֹת שֶׁחֻדְּשׁוּ" (And there are yet other mitzvot that were innovated/instituted)⁹: The use of "מצוות" (mitzvot) for Rabbinic enactments is critical. It implies a true command, not merely a recommendation. The verb "חודשו" (were innovated/renewed) highlights their post-Sinaitic origin.
• "וְהֵן אֵינָן נֶחֱשָׁבוֹת תּוֹסֶפֶת" (And these are not considered an addition)¹⁰: This is the direct refutation of the Bal Tosif challenge. They are mitzvot, yet not additions.
• "שֶׁאֵין נָבִיא רַשַּׁאי לְחַדֵּשׁ דָּבָר וְלוֹמַר שֶׁהַקָּדוֹשׁ בָּרוּךְ הוּא צִוָּנוּ" (That a prophet is not permitted to introduce a new measure and say that the Holy One, blessed be He, commanded us)¹¹: This is the pivot. The prohibition of Bal Tosif hinges on the attribution of the command. If one claims God commanded it at Sinai (or subsequently as a de'Oraita matter), it's Bal Tosif.
• "אֲבָל בֵּית דִּין עִם הַנָּבִיא שֶׁבְּדוֹר... תִּקְּנוּ וְצִוּוּ" (However, if a court, together with the prophet of that age... ordained and commanded)¹²: The shift from "God commanded" to "court ordained and commanded" is the linchpin. The authority is human (albeit divinely sanctioned), not a new divine revelation.
• "כְּדֵי לְהַזְכִּיר גְּבוּרוֹת הַקָּדוֹשׁ בָּרוּךְ הוּא" (In order to recall the praises of the Holy One, blessed be He)¹³: The Rambam provides the raison d'être for these Rabbinic commands – often for remembrance (zecher l'nes), or as a protective fence (seyag laTorah). This purpose-driven aspect reinforces their Rabbinic origin and prevents them from being misconstrued as new divine mitzvot.

The Rambam's meticulous phrasing distinguishes between the content of a command and its source of authority. Rabbinic mitzvot are real mitzvot because Lo Tasur makes them so, but they avoid Bal Tosif because their origin is openly acknowledged as Rabbinic, not Sinaitic.

Readings

The Rambam's succinct articulation here is a distillation of a much broader and deeper halachic principle, one he elaborates upon significantly in his Sefer HaMitzvot and Hilchot Mamrim. Understanding this passage requires engaging with his foundational methodology and the critiques leveled against it by other Rishonim, most notably the Ramban.

1. The Rambam: Lo Tasur as the Enabler, Bal Tosif as the Boundary of Attribution

The Rambam's position, as expressed in the text and more expansively in Sefer HaMitzvot (Shoresh Rishon and Shoresh Sheni)¹⁴ and Hilchot Mamrim (1:1-2:2)¹⁵, hinges on a precise definition of Bal Tosif. For the Rambam, the prohibition of Bal Tosif is violated only when one claims that a new commandment, or an alteration to an existing one, was divinely commanded and is therefore min haTorah (of Torah origin).

He states clearly in Hilchot Mamrim:

"כל מי שיוסיף על דברי תורה או יגרע מהם הרי זה עובר בלאו שנאמר לא תוסיף עליו ולא תגרע ממנו. במה דברים אמורים, בזמן שיוסיף ויאמר שהשם צוה בדבר זה, או יגרע ויאמר שהשם בטל מצוה זו. אבל אם עשה סייג לדבריו לא עבר בלאו."¹⁶ (Anyone who adds to the words of the Torah or subtracts from them transgresses a negative commandment, as it is stated, "You shall not add to it nor subtract from it." When does this apply? When one adds and says that God commanded this matter, or subtracts and says that God nullified this mitzvah. But if one makes a fence for His words, one does not transgress a negative commandment.)

This is the bedrock of his understanding. Rabbinic gezeirot, takanot, and minhagim are explicitly acknowledged as human enactments, albeit ones mandated by the Torah itself through the positive commandment of Lo Tasur (Deuteronomy 17:11)¹⁷. The Sages do not claim a new prophecy or a new divine command; rather, they exercise their inherent interpretive and legislative authority, which was granted at Sinai. The Megillah reading, Chanukah lights, and Netilat Yadayim are called mitzvot because the Torah commands us to obey the Sages, and thus, observing their decrees becomes a fulfillment of a Torah mitzvah (the mitzvah of Lo Tasur).

The Rambam further clarifies that the authority of Beis Din extends even to interpreting the Torah in ways that might seem counter-intuitive, as long as they are acting within the framework of received tradition and the Lo Tasur mandate. This allows for dynamic halachic development without undermining the immutability of the Sinaitic revelation. The dikduk in our text, "He is not saying that the Holy One, blessed be He, commanded us... Instead, we are saying that the prophets and the courts ordained and commanded," perfectly encapsulates this distinction. The "why" of the Rabbinic enactment (e.g., zecher l'nes) provides its context and prevents it from being confused with a Sinaitic command.

2. The Ramban: Bal Tosif as a Prohibition on Altering the Mode or Text

Nachmanides (Ramban), in his Hasagot (critiques) to Sefer HaMitzvot, specifically on Shoresh Rishon¹⁸, offers a different interpretation of Bal Tosif. While he agrees with the Rambam on the general authority of Chazal, his understanding of Bal Tosif is more nuanced.

The Ramban argues that Bal Tosif is not primarily concerned with the addition of new obligations per se, but rather with altering the mode of performance of an existing Torah mitzvah or adding to the text of the Torah itself. For instance, adding a fifth parsha to tefillin or a fifth species to lulav would be a violation of Bal Tosif because it misrepresents the divine command by changing its prescribed form. He writes:

"אבל אם יוסיף במצות עצמה, כגון שיעשה חמש פרשיות בתפילין או חמישה מינין בלולב, זהו לא תוסיף."¹⁹ (But if one adds to the mitzvah itself, such as making five sections in tefillin or five species in a lulav, that is Bal Tosif.)

However, if the Sages institute a new observance, such as Hallel on Rosh Chodesh or Megillah reading, and explicitly state that it is deRabanan, it is not a violation of Bal Tosif. This is because these new enactments are distinct mitzvot and do not purport to be additions or alterations to existing Torah mitzvot. They stand on their own as Rabbinic obligations, derived from the general principle of obeying the Sages (Lo Tasur).

While the Ramban criticizes the Rambam's broad application of Bal Tosif to any claim of divine command for new mitzvot, in practice, their conclusions regarding the permissibility of Mitzvot DeRabanan are often similar. The key difference lies in the theoretical underpinning: Rambam focuses on the attribution (claiming God commanded it), while Ramban focuses on the nature of the addition (altering an existing mitzvah vs. creating a new, distinct Rabbinic one). The Ramban's view implicitly allows for new Rabbinic mitzvot more readily, as long as they don't masquerade as Torah mitzvot or modify them. His critique is therefore more about the Rambam's definition of Bal Tosif than about the legitimacy of Rabbinic decrees.

3. Rashba: Mitzvah by Proxy – The Power of Lo Tasur

The Rashba, in his Responsa (e.g., Shut HaRashba 1:9)²⁰, further elaborates on the concept of Mitzvot DeRabanan. He addresses the question of why we refer to Rabbinic enactments as "mitzvot" at all. His answer strongly aligns with the Rambam's framework, emphasizing the pivotal role of Lo Tasur.

The Rashba posits that Rabbinic decrees are indeed "mitzvot" because their observance constitutes the fulfillment of a Torah commandment: the mitzvah to obey the Sages ("לא תסור מן הדבר אשר יגידו לך"). Therefore, when one lights Chanukah candles or reads the Megillah, one is not directly fulfilling a mitzvah commanded by God at Sinai about Chanukah or Purim. Rather, one is fulfilling the Torah's command to listen to and implement the decrees of the Sages. This makes the Rabbinic enactment a mitzvah by proxy, or a derivative mitzvah, whose source is ultimately Sinaitic, but whose specific content is Rabbinic.

This perspective beautifully reconciles the terminology. It explains how something can be called a "mitzvah" (carrying divine sanction and spiritual weight) while simultaneously being "deRabanan" (originating from human wisdom and authority). The Rashba's contribution solidifies the Rambam's understanding of Lo Tasur as the overarching principle that legitimizes and elevates Rabbinic legislation. The Sages are not merely advisors; they are divinely empowered legislators whose directives become binding through a direct Torah command.

4. Maharal of Prague: The Inherent Divinity of Rabbinic Authority

The Maharal of Prague, in his Tiferet Yisrael (Chapter 11)²¹, offers a more philosophical and ontological perspective on the authority of Chazal. He views the Sages not as "adding" to the Torah, but as revealing its deeper, inherent truths and applying its principles in a way that was always latent within the divine revelation.

For Maharal, the Torah given at Sinai was not a static, finite text, but a living, dynamic entity. The Sages, through their profound understanding and connection to the divine, are uniquely positioned to draw out these truths. Their gezeirot and takanot are not external impositions but rather necessary actualizations of the Torah's own will. The command of Lo Tasur is not just a legal injunction; it reflects the ontological necessity of Rabbinic authority for the Torah's continued vitality and relevance in every generation.

Maharal argues that the Sages' enactments are like a "fence" (seyag laTorah) not merely to protect the Torah, but because the Torah itself implicitly requires such protection and extension. Without the interpretive and legislative activity of the Sages, the Torah would be incomplete or unable to function in a changing world. Therefore, the Sages do not transgress Bal Tosif because their actions are an integral part of the Torah's own unfolding, a continuous revelation of its infinite depth. They are not adding something foreign; they are bringing forth what was always within. This elevates Rabbinic authority beyond mere legalistic obedience to a profound spiritual and intellectual partnership in the ongoing revelation of God's will.

Friction

The Grand Kushya: The Metaphysics of Bal Tosif vs. Lo Tasur

The most potent kushya arising from the Rambam's position, and indeed from any attempt to reconcile Rabbinic authority with Bal Tosif, is a fundamental one: If the Torah explicitly prohibits adding any command, how can Chazal institute any new observances, even if they explicitly label them "Rabbinic"? The very act of creating a new obligation, regardless of its attribution, feels like an addition to the corpus of divine commands.

Consider the following:

1. Semantic Overlap: Rabbinic mitzvot often mirror Torah mitzvot in their structure and language. For example, the mitzvah to light Chanukah candles, say a bracha on them, and count them as eight days, strongly resembles a Torah mitzvah in form and spiritual weight. If I say "God commanded us to light Chanukah candles," how is that different from saying "The Sages commanded us to light Chanukah candles, and the Torah commanded us to listen to the Sages"? The end result for the individual is an obligation with divine sanction.
2. The Scope of "Addition": Does "לא תוסיף" only refer to claiming divine origin for the new mitzvah, or does it also encompass any new obligation that increases the burden or scope of religious observance? If a Beis Din institutes a new fast day, for example, it adds a burden. Is this not an "addition" to the divine expectation of a Jew?
3. The "Right is Left" Paradox: The Gemara in Sanhedrin 88b²² famously states regarding Lo Tasur: "אפילו אומרים לך על ימין שהוא שמאל ועל שמאל שהוא ימין" (Even if they tell you that right is left and left is right). This seemingly grants Beis Din absolute authority to reinterpret or even contradict what appears plain. If their authority is so absolute, what meaningful boundary does Bal Tosif still impose? Does it become a mere linguistic technicality, rather than a substantive prohibition against altering God's law?

This kushya challenges the very essence of the Rambam's distinction. Is the "attribution" clause sufficient to safeguard the integrity of Bal Tosif, or does it create a loophole that effectively neuters the prohibition? The concern is that if Rabbinic enactments are so readily permitted under the umbrella of Lo Tasur, then Bal Tosif loses its teeth as a guardian against human meddling with divine law. It appears that the Sages are adding to the mitzvot, even if they call them Rabbinic, and that such an "addition" should fall under the purview of Bal Tosif.

The Best Terutz (or Two): Rambam's Precision and the Nature of Authority

The resolution lies in a profound understanding of the Rambam's precise definitions and the distinct nature of divine versus Rabbinic authority.

Terutz 1: The Integrity of Sinaitic Revelation – The Core of Rambam's Distinction

The Rambam's terutz, articulated in our text and in Hilchot Mamrim²³, maintains that Bal Tosif specifically protects the integrity and immutability of the Sinaitic revelation. The 613 mitzvot are a closed corpus, divinely ordained and unalterable. To claim that God Himself commanded a 614th mitzvah, or that one of the 613 was rescinded, is a direct challenge to God's omnipotence and the perfection of His Torah. This is Bal Tosif.

However, Mitzvot DeRabanan operate on a different plane. They are not presented as new divine commands, but as human enactments made under divine authorization. The Torah itself, through the mitzvah of Lo Tasur, empowers the Sages to legislate for the Jewish people. This is a crucial distinction:

• Source of Obligation: The obligation to light Chanukah candles does not come directly from God's mouth at Sinai for Chanukah itself. It comes from the Sages' decree, which is then made binding by the Torah's command to obey the Sages. Thus, the primary source of the obligation for any Rabbinic mitzvah is Lo Tasur, a Torah mitzvah itself.
• Purpose and Context: Rabbinic mitzvot are always instituted with specific, articulated purposes: to create a "fence" around the Torah (seyag laTorah), to commemorate miracles (zecher l'nes), or to ensure the proper functioning of society (takanat ha'olam). These purposes are inherently distinct from the eternal, immutable purposes of the 613 mitzvot. The Sages do not claim a new category of divine command; they apply existing divine principles to new situations or create protective measures around them.
• Dynamic vs. Static: The 613 mitzvot are static and eternal. The Mitzvot DeRabanan are dynamic and subject to the changing needs of the generations, within the bounds of Lo Tasur. A future Beis Din can, in theory, nullify or modify a Rabbinic decree if circumstances warrant, something impossible for a Torah mitzvah. This inherent flexibility underscores their Rabbinic, not divine, origin.

Thus, the Rambam's distinction is not a mere technicality, but a profound theological and halachic principle. Bal Tosif protects God's unique role as the ultimate Lawgiver of the unchanging Torah. Lo Tasur defines humanity's divinely mandated role in interpreting, safeguarding, and implementing that Torah through the ongoing authority of its Sages. The Sages are not adding to God's commands; they are fulfilling one of His commands (to obey them) by instituting their own decrees.

Terutz 2: The Ramban's "Mode of Performance" Distinction

While the Rambam emphasizes attribution, the Ramban's terutz (as presented in his Hasagot to Sefer HaMitzvot) offers a complementary, though distinct, resolution, focusing on the nature of the "addition."

For the Ramban, Bal Tosif is primarily concerned with:

1. Adding to the Text of the Torah: Directly inserting new verses or commands into the written word of God.
2. Altering the Mode of Performance of an Existing Mitzvah: This is the core of his position. If the Torah specifies a particular way to perform a mitzvah (e.g., four species for lulav, four parshiot for tefillin), Bal Tosif prohibits adding a fifth, as this would distort the divine instruction and imply that the original instruction was incomplete or incorrect.

Under this understanding, Rabbinic mitzvot like Chanukah or Purim do not violate Bal Tosif because they are new, distinct observances. They do not claim to be the same mitzvah as a Torah mitzvah with an added component. They are entirely separate entities. Lighting Chanukah candles is not an "addition" to the mitzvah of lighting the Menorah in the Temple; it is a new mitzvah to commemorate a different event.

The strength of the Ramban's approach is its clear-cut nature: is it an addition to an existing mitzvah's form, or is it a new, separate mitzvah? If it's the latter, and explicitly declared Rabbinic, it's permitted by Lo Tasur. This avoids the need for the Rambam's nuanced "attribution" test to such an extreme degree, though the underlying principle of not claiming divine origin for new mitzvot remains. Both Rishonim, in their own ways, provide robust frameworks for understanding how halacha can flourish through Rabbinic agency without compromising the immutability of the Torah.

Intertext

The Rambam's discussion on Bal Tosif and Lo Tasur is not an isolated conceptual exercise; it is deeply rooted in broader Rabbinic discourse and finds its primary textual sources in the Torah itself and classical Rabbinic literature.

1. Deuteronomy 17:8-11 and the Authority of the Sanhedrin

The fundamental source for the authority of the Sages, which underpins the legitimacy of Mitzvot DeRabanan, is found in Deuteronomy 17:8-11:

"כִּי יִפָּלֵא מִמְּךָ דָבָר לַמִּשְׁפָּט... וְקַמְתָּ וְעָלִיתָ אֶל הַמָּקוֹם אֲשֶׁר יִבְחַר יְהוָה אֱלֹהֶיךָ בּוֹ. וּבָאתָ אֶל הַכֹּהֲנִים הַלְוִיִּם וְאֶל הַשֹּׁפֵט אֲשֶׁר יִהְיֶה בַּיָּמִים הָהֵם וְדָרַשְׁתָּ וְהִגִּידוּ לְךָ אֵת דְּבַר הַמִּשְׁפָּט. וְעָשִׂיתָ עַל פִּי הַדָּבָר אֲשֶׁר יַגִּידוּ לְךָ מִן הַמָּקוֹם הַהוּא אֲשֶׁר יִבְחַר יְהוָה וְשָׁמַרְתָּ לַעֲשׂוֹת כְּכֹל אֲשֶׁר יוֹרוּךָ. עַל פִּי הַתּוֹרָה אֲשֶׁר יוֹרוּךָ וְעַל הַמִּשְׁפָּט אֲשֶׁר יֹאמְרוּ לְךָ תַּעֲשֶׂה לֹא תָסוּר מִן הַדָּבָר אֲשֶׁר יַגִּידוּ לְךָ יָמִין וּשְׂמֹאל."²⁴ (If a matter is too difficult for you to judge... you shall arise and go up to the place that the Lord your God will choose. And you shall come to the Levitic priests and to the judge who will be in those days, and you shall inquire, and they will tell you the word of judgment. And you shall act according to the word that they tell you from that place that the Lord will choose, and you shall be careful to do according to all that they instruct you. According to the Torah that they instruct you, and according to the judgment that they tell you, you shall do; you shall not deviate from the word that they tell you, right or left.)

This passage, particularly the concluding phrase "לֹא תָסוּר מִן הַדָּבָר אֲשֶׁר יַגִּידוּ לְךָ יָמִין וּשְׂמֹאל" (You shall not deviate from the word that they tell you, right or left), is the bedrock of the mitzvah of Lo Tasur. The Rambam explicitly references this verse in our text to justify the obligation to observe Mitzvot DeRabanan. This mitzvah bestows upon the Sanhedrin (the supreme Rabbinic court) the authority to interpret existing laws, clarify ambiguities, and—crucially for our discussion—institute gezeirot and takanot.

The Sifrei Devarim 153 on this verse famously interprets "ימין ושמאל" as: "אפילו נראה בעיניך שימין זה שמאל ושמאל זה ימין" (Even if it appears in your eyes that right is left and left is right)²⁵. This hyperbolic statement underscores the absolute nature of the obligation to obey the Beis Din HaGadol, even when their reasoning is not immediately apparent or seems counter-intuitive. This interpretive tradition reinforces the idea that the Sages' authority is not merely advisory but truly legislative, and that the Torah commands obedience to their rulings.

2. Sanhedrin 88b and the Limits of Prophecy

The Gemara in Sanhedrin 88b delves into the nuances of Lo Tasur and Bal Tosif, particularly concerning the role of a prophet:

"שכל הנביאים כולן לא באו אלא לחזק דברי תורה... אבל למעט וללמוד מכלל ופרט - לאו, למעט וללמוד מכלל ופרט - לאו. אלא מה יעשה הנביא? אם אמר לך נביא: עבור על דברי תורה, שמע לו, אלא אם כן נביא שקר הוא. אלא אם כן אמר לך: לך ועבוד עבודה זרה, אל תשמע לו."²⁶ (All the prophets came only to strengthen the words of the Torah... But to diminish or to derive from a general principle and a specific detail - no. To diminish or to derive from a general principle and a specific detail - no. So what should a prophet do? If a prophet tells you: transgress the words of the Torah, listen to him, unless he is a false prophet. But if he tells you: go and worship idolatry, do not listen to him.)

This passage, though complex and subject to various interpretations (especially the part about transgressing Torah), is crucial for the Rambam's understanding. The Gemara explicitly states that prophets come "לחזק דברי תורה" (to strengthen the words of the Torah), not to diminish or add to them. It reinforces the idea that the Torah is complete and immutable. The Rambam's formulation in our text—that a prophet is not permitted to "say that the Holy One, blessed be He, commanded this mitzvah to us and that it should be added to the Torah's mitzvot"²⁷—is a direct application of this Gemara's principle. Prophecy, post-Sinai, is for reinforcement and inspiration, not for introducing new mitzvot or nullifying existing ones min haTorah.

The Rambam, in Hilchot Yesodei HaTorah 9:1, further solidifies this by stating that a prophet who claims to bring a new mitzvah (or remove an old one) is a Navi Sheker (false prophet) and is liable for the death penalty²⁸. This strict delineation ensures that the 613 mitzvot remain eternally fixed, while simultaneously allowing for the dynamic legislative capacity of the Beis Din under the auspices of Lo Tasur. The distinction is between divine legislation (closed) and Rabbinic legislation (open, but Torah-sanctioned).

Psak/Practice

The Rambam's theoretical reconciliation of Bal Tosif and Lo Tasur has profound and enduring implications for halacha lema'aseh (practical halacha) and meta-psak heuristics.

The Foundation of Rabbinic Authority

Fundamentally, the Rambam's approach provides the halachic bedrock for the binding nature of all Mitzvot DeRabanan. Without this clear framework, the legitimacy of practices like Chanukah, Purim, Netilat Yadayim, Eruvin, and countless gezeirot (like the prohibition against eating bread baked by a gentile, Pas Akum) would be tenuous. We observe these not as mere customs, but as divinely mandated obligations, because the Torah itself, through Lo Tasur, commands us to obey the Sages who instituted them. This elevates Rabbinic decrees to a status that, while distinct from de'Oraita, is nevertheless obligatory from a Torah perspective.

Guiding Future Halachic Development

The Rambam's distinction serves as a crucial heuristic for subsequent generations of Poskim (halachic decisors) and Batei Din. It establishes parameters for innovation:

• No Claim of New Torah Mitzvah: A Beis Din can institute new takanot or gezeirot (e.g., in response to new technologies or societal changes), but it can never claim that these are min haTorah or that God directly commanded them. The source of authority must always be acknowledged as Rabbinic, even if rooted in Lo Tasur.
• Purpose-Driven Enactments: Rabbinic enactments must generally have a clear raison d'être – seyag laTorah, zecher l'nes, takanat ha'olam, etc. This prevents arbitrary or frivolous additions to religious practice.
• The Power to Annul: The principle that a Beis Din cannot nullify a decree of a previous Beis Din unless it is greater in wisdom and number (Ein Beis Din Yachol Levatel Divrei Beis Din Chaveiro Ela Im Ken Gadol Mimenu B'Chochma U'V'Minian)²⁹ also operates within this framework. This ensures continuity and stability in Rabbinic law, while still allowing for necessary adjustments or revocations if a later court possesses the requisite authority.

The Rambam's synthesis ensures that the Torah, as given at Sinai, remains immutable and complete, while simultaneously empowering the living tradition of Rabbinic Judaism to grow, adapt, and respond to the spiritual and practical needs of the Jewish people across generations. It's a testament to the dynamic yet fixed nature of Halakha.

Takeaway

The Rambam's genius lies in reconciling the immutability of Sinaitic revelation with the dynamism of Rabbinic authority. He teaches that Bal Tosif safeguards the divine source of the 613 mitzvot, while Lo Tasur provides the divine mandate for the Sages to legislate, thereby ensuring the Torah's eternal relevance and our binding obligation to their decrees.

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¹ Deuteronomy 13:1. ² Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part A). ³ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part B). ⁴ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part C, referencing Deuteronomy 17:11). ⁵ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part C, referencing Deuteronomy 13:1). ⁶ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part D). ⁷ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part E, referencing Deuteronomy 4:7). ⁸ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part E). ⁹ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part B). ¹⁰ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part C). ¹¹ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part C). ¹² Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part D). ¹³ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part E). ¹⁴ Rambam, Sefer HaMitzvot, Shoresh Rishon, and Shoresh Sheni. ¹⁵ Rambam, Mishneh Torah, Hilchot Mamrim 1:1-2:2. ¹⁶ Rambam, Mishneh Torah, Hilchot Mamrim 2:9. ¹⁷ Deuteronomy 17:11. ¹⁸ Ramban, Hasagot to Sefer HaMitzvot, Shoresh Rishon. ¹⁹ Ramban, Hasagot to Sefer HaMitzvot, Shoresh Rishon s.v. "והשורש הראשון". ²⁰ Rashba, Shut HaRashba, Part 1, Responsum 9. ²¹ Maharal of Prague, Tiferet Yisrael, Chapter 11. ²² Sanhedrin 88b. ²³ Rambam, Mishneh Torah, Hilchot Mamrim 2:9. ²⁴ Deuteronomy 17:8-11. ²⁵ Sifrei Devarim 153, s.v. "לא תסור". ²⁶ Sanhedrin 88b. ²⁷ Mishneh Torah, Negative Mitzvot 1-365 (Concluding Section, part C). ²⁸ Rambam, Mishneh Torah, Hilchot Yesodei HaTorah 9:1. ²⁹ Mishnah Eduyot 1:5; Rambam, Mishneh Torah, Hilchot Mamrim 2:2.