Sandwiched between the linchpin prohibition of avodah zarah that is equivalent to rejecting the entire Torah and the delineation of the parameters of the equally important challenge of false prophecy, the Torah briefly (13:1) inserts a second reference (see Devarim 4:2) to the linked transgressions of baal tosif and baal tigra. According to the Masoretic division of the parshiyot, these issurim constitute the coda of the idolatry presentation, further highlighting the apparent pivotal significance of the dual proscriptions to tamper with Biblical law.
While some mefarshim account for the linkage to avodah zarah in ways that downplay the connection and provide a more pragmatic explanation for the continuity of the parshiyot (See, for example, the explanation of Akeidat Yitzchak, the first view cited by Abarbanel, the remarks of Seforno both on 4:2 and 13:1, and especially the comments of Rav Yosef Albo, Sefer ha-Ikkarim 3:14 that we shall soon explore), the majority of the commentators do ascribe great importance to baal tosif and baal tigra in a manner that would fully justify their context. The indispensable role of these intriguing issurim (see, for example, Keli Yakar, Devarim 4:2) is particularly promulgated by the Rambam, for whom remarkably it attains the status of a tenet of faith!
Rambam invokes these lavin and our verse as the source for the ninth of thirteen ikkarei Emunah (tenets of faith) affirming the immutability of the Torah and halachah (Peirush ha-Mishneh, introduction to perek Chelek, no. 9 [see R’ Y. Kapach edition, n. 77 with respect to the divergent formulation that appears in the earlier printed versions])! In Hilchot Melachim (11:3) Rambam again links immutability with the prohibition to add or subtract from the mitzvot. Moreover, he equates one who violates by tampering with halachic norms with the infraction of “megalah panim ba-halachah”, identifying both as heretical postures. He declares: “veikar hadevarim kachah hein: she-haTorah hazot ein chukehah u-mishpateha mishtanim leolam uleolemei olamim ve-ein mosifin aleihen velo goriin meihen, vekol hamosif o goreia o shegilah panim ba-Torah vehotzi hadevarim shel mitzvot mipeshutan harei zeh bevadai rasha veapikores.” Already in Hilchot Yesodei haTorah (9:1), he utilizes the terminology associated with these prohibitions to signify the Torah’s unchanging character (“davar barur umefurash ba-Torah shehi mitzvah omeded leolam uleolmei olamim, ein lah lo shinui ve-lo giraon velo tosefet”), again founding this tenet on our verse in parshat Reeh. Rambam ubiquitously refers to baal tosif and in locations that are strategically important. This theme sets the tone of Yad ha-Chazakah (the conclusion of his petichah after the minyan hakatzar, as well as Hilchot Yesodei haTorah), and is revisited in crucial passages (Hilchot Mamrim 2:9, 4:3, Hilchot Melachim 11:3) at the culmination of his work. Moreover, while the Sifrei (Reeh, see Rashi, Ramban Devarim 4:2, Rashi 13:1, Raavad, Hilchos Mamrim 2:9, R’ Albo, Ikkarim 3:14) and Talmud (Sanhedrin 88a, R.H. 28b etc.) focus on tampering internally within mitzvot (adding or subtracting a min of the lulav, extending mitzvat sukkah an extra day, adding a berachah to birkat kohanim etc.), Rambam extends baal tosif to adding to the complement of taryag mitzvot! [See also Ramban Devarim 4:2 and the intriguing comment of the Gera in Aderet Eliyahu 13:1] This innovative expansion, which triggered controversy (See Raavad, Hilchos Mamrim op cit, and R’ Albo op cit) undoubtedly underpinned his conviction that baal tosif-bal tigra is a facet of and source for the immutability tenet. While Rambam in several halachot also relates to the more internal baal tosif tampering, he certainly primarily accentuates the effort to revise the broad halachic system by addition or subtraction of norms. Evidently, Rambam viewed both forms of baal tosif as commonly undermining the fundamental integrity, authenticity, and divinity of the halachic system. [I hope to elaborate this point elsewhere in a discussion of Rambam’s striking omission of the malkot punishment for violating baal tosif.]
Different facets of Rambam’s view were sharply criticized. In addition to R’ Albo’s fundamental objection to some aspects of Rambam’s perspective on immutability, he is especially adamant in dismissing the relevance of baal tosif-bal tigra to this issue, arguing that these transgressions are exclusively about the internal implementation of individual mitzvoth - “lo ba lehazhir al kelal mitzvot ha-Torah ela al techunat asiyatan bilvad”. At the same time, ironically, R. Yosef Albo provides significant insight (based on his expansion of broader comments in Moreh Nevuchim [see III:34, but compare also to III:41]) into Rambam’s linkage between halachah’s immutability and baal tosif. He notes that harmony and perfection do not abide additions any more than they allow subtractions. Hence, perfect Divine Torah (“Torat Hashem temimah”, Tehilim 19:8) can never be changed.
Abarbenel (Devarim 13:1) reacting to the debate between Rambam and Albo, formulates a different difficulty with Rambam’s linkage. He notes that baal tosif and baal tigra are issurim, not ikarim, as they focus on the propriety of man’s actions not on the principle of immutability. Moreover, it is theoretically conceivable that Hashem can alter His Torah even if man has no such authority or capacity. He rejects the conclusion that Rambam included baal tosif in the tenet of immutability or that it even served as its source. Alternatively, he posits that Rambam may have intended to demonstrate immutability not from the prohibitions of baal tosif and baal tigra, but from the Torah’s formulation in the first part of the verse that introduces the twin issurim - “eis kol hadavar asher anochi metzaveh etchem, oto tishmeru laasot”- which he interpreted as a declaration that the mitzvot already revealed are the only mitzvot in all eras, that the mitzvot are unchangeable. [In fact, while the Rambam does quotes the entire verse in Hilchot Yesodei ha-Torah, he only cites baal tosif and baal tigra in his presentation in Peirush ha-Mishnayot.] Abarbanel alludes to the more expansive discussion in his Rosh Amanah (ch. 3, 13 - beheter safek harevii), in which he analyzes the tenets of faith. Like R’ Albo, Abarbanel in Rosh Amanah perceived that Rambam’s position derives from the implications of Torah’s divinity and perfection that preclude internal tampering with mitzvah performance as well as the effort to add more mitzvot. Although he denies that baal tosif itself constitutes an ikar, in both contexts he ultimately concedes, unlike R’ Albo, that there is an integral connection between immutability and baal tosif. In his commentary, he compellingly formulates baal tosif as a manifestation of halachah’s immutability - “ve-lachen lo tosifu aleihem velo tigreu meihem ki bedavar asher asah Hashem yitaleh laamod lefanav tamid eich yosifu oh yigreu benei adam milibam davar”! In Rosh Amanah, he goes a step further, asserting that baal tosif demonstrates or reinforces immutability. In both contexts, the conclusion of the verse derives from the fundamental principle of immutability-Divinity that it asserts.
The notion that baal tosif constitutes a pivotal principle that is fundamentally predicated on the Torah’s divinity and perfection, undoubtedly furthered by Rambam’s striking perspective, resonates in the formulations of other authorities, as well. Sefer ha-Hinuch (no. 454) and the author of Sefer ha-Batim (Migdal David no. 314) emphasize Torah’s holistic self-sufficiency - “Hashem metzaveh be-tachlit hasheleimut’ ve-kol maasav sheleimim ve-tovim, ve-tosefet bahem hisaron, ve-kol shekein hagiraon” (Chinuch). The Radvaz (Metzudat David no. 572 after his initial pragmatic suggestion) grounds baal tosif in the intrinsic sanctity and divinity of cheftza shel Torah. Tolerating even tosefet is tantamount to no less than altering one of Hashem’s divine names, or tolerating a reconfiguration of the spiritual-mystical super-structure of the world! [Radvaz integrates this core conception with his own position that ikarim are superfluous, as the implications of tosefet and certainly giraon render all violations a breach of principle.]
The idea that the entire halachic system constitutes a kind of religious homeostasis or perfect balance reinforces the conclusion that baal tosif-bal tigra transcends routine transgressions. Abarbanel (parshat Ekev) notes that the Torah occasionally is referred to in the singular-“mitzvah”- precisely because of its holistic integrity. He ties this notion to larger principles like yichud Hashem, mishpat ehad yihyeh lachem (the ideal of uniform normative observance), the symbolic significance of the count of 613 mitzvot comprised of 248 eivarim and 365 gidin (or days of the year), and other manifestations that accentuate the comprehensiveness and interconnection of halachic law. Even absent Rambam’s ambitious conclusion that baal tosif-bal tigra is a facet of the tenet of the immutability of halachah, its prominent location in parshat Reeh (as well as in Vaetchanan … see Chizkuni, Devarim 4:2) emerges as compelling and inspiring. The enduring legacy of Torat Moshe, the foundation of vibrant Jewish life, despite countless transformations and challenges over time and in a wide range of geographic settings, is the ultimate testament to this pivotal theme.