Mishneh Torah, Foundations of the Torah 9

Sugya Map

• Issue: The immutability of Torah law and the defined scope of prophetic authority.
• Nafka Mina(s):
  • Distinguishing a true prophet from a false one (מיתת נביא שקר).
  • The halachic validity of hora'at sha'ah (temporary abrogation) versus permanent change.
  • The foundation of Torah Sheb'al Peh's authority ("לא בשמים היא").
• Primary Sources: Devarim 13:1 ("לא תוסיף עליו ולא תגרע ממנו"), Devarim 29:28 ("הנסתרות לה׳ אלקינו והנגלות לנו ולבנינו עד עולם לעשות את כל דברי התורה הזאת"), Devarim 30:12 ("לא בשמים היא"), Devarim 18:18-19 (role of future prophet), Melachim I 18 (Elijah on Carmel), Malachi 3:22 ("זכרו תורת משה עבדי").

Text Snapshot

ונאמר לא בשמים היא, הא למדת שאין נביא רשאי לחדש דבר מעתה.¹

...אם נביא... ציוה לעבור על אחת מכל מצות התורה או על מצוות רבות, בין קלות בין חמורות, לפי שעה – שומעין לו.²

...אפילו יטע עץ אשירה ויקריב לה, הרי זה יאמר: על פי ה' אני עושה היום.³

The phrase "לא בשמים היא" – "It is not in the heavens" – is pivotal, sealing the Torah's eternal nature and removing its interpretation and legislation from direct heavenly intervention post-Sinai. The immediate juxtaposition with a prophet's temporary command for transgression (הוראת שעה) highlights the critical distinction between outright abrogation and a time-bound suspension.

Readings

Tziunei Maharan: The Source of "לא בשמים היא"

The Tziunei Maharan⁴ on this Rambam points to Gemara Temurah 16a as the source for the Rambam's use of "לא בשמים היא" in defining the prophet's limited authority. There, R. Yehoshua explicitly uses this verse to counter the notion that a prophet can innovate law, citing it in the context of forgotten halachot after Moshe's passing, implying that even for lost laws, we don't turn to prophecy but to traditional interpretation.

Seder Mishnah: Defending Torah's Immutability

The Seder Mishnah⁵ vehemently defends Rambam's assertion of Torah's absolute immutability against the Sefer HaIkkarim (R. Yosef Albo), who suggests that certain mitzvot could theoretically change. The Seder Mishnah argues that if mitzvot were subject to change, we could never definitively identify a false prophet who claims to abrogate a mitzvah, as it would always be possible that Hashem indeed commanded the change. This underscores the theological necessity of Torah's eternality for the very definition of prophecy.

Friction

The tension lies in reconciling the Torah's eternal immutability ("לא תוסיף ולא תגרע") with the allowance for hora'at sha'ah (temporary prophetic abrogation of a mitzvah) as exemplified by Elijah on Mount Carmel. If "לא בשמים היא" means no new mitzvot, how can a prophet command a transgression, even temporarily?

The Rambam resolves this by distinguishing between changing or adding to the Torah (which is forbidden and constitutes a false prophet) and temporarily suspending a mitzvah for a specific, divine purpose, often to avert a greater spiritual danger (e.g., Elijah countering idolatry). This temporary suspension does not deny the mitzvah's eternal validity but rather prioritizes a higher divine will for a limited time.

Intertext

The classic parallel is the Tanur Shel Achnai sugya in Bava Metzia 59b. There, R. Yehoshua famously declares "לא בשמים היא" to assert that once the Torah was given, halacha is determined by the Sages' dialectic, not by divine voices or miracles. While Rambam applies it here specifically to prophecy, the underlying principle of human agency in halachic interpretation is consonant.

Psak/Practice

This sugya establishes a fundamental heuristic in halachic thought: no prophet, no matter how great, can permanently alter Torah law. Temporary dispensations (hora'at sha'ah) are only permissible for specific, limited circumstances (excluding idolatry), and critically, they must come from an established prophet. This ensures the integrity and eternality of Torah while allowing for divine intervention in extraordinary circumstances.

Takeaway

The Torah is eternally immutable; prophecy cannot add or subtract mitzvot, but an established prophet can temporarily suspend a mitzvah (except idolatry) for a critical, time-bound purpose.

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¹ Mishneh Torah, Foundations of the Torah 9:1:1. ² Mishneh Torah, Foundations of the Torah 9:1:3. ³ Mishneh Torah, Foundations of the Torah 9:1:4. ⁴ Tziunei Maharan on Mishneh Torah, Foundations of the Torah 9:1:1. ⁵ Seder Mishnah on Mishneh Torah, Foundations of the Torah 9:1:1.