מדע
הלכות יסודי התורה
פרק ט

Halacha

הלכה א
דָּבָר בָּרוּר וּמְפֹרָשׁ בַּתּוֹרָה שֶׁהִיא מִצְוָה עוֹמֶדֶת לְעוֹלָם וּלְעוֹלְמֵי עוֹלָמִים אֵין לָהּ לֹא שִׁנּוּי וְלֹא גֵּרָעוֹן וְלֹא תּוֹסֶפֶת שֶׁנֶּאֱמַר (דברים יג א) "אֵת כָּל הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם אֹתוֹ תִשְׁמְרוּן לַעֲשׂוֹת לֹא תֹסֵף עָלָיו וְלֹא תִגְרַע מִמֶּנּוּ". וְנֶאֱמַר (דברים כט כח) "וְהַנִּגְלֹת לָנוּ וּלְבָנֵינוּ עַד עוֹלָם לַעֲשׂוֹת אֶת כָּל דִּבְרֵי הַתּוֹרָה הַזֹּאת". הָא לָמַדְתָּ שֶׁכָּל דִּבְרֵי תּוֹרָה מְצֻוִּין אָנוּ לַעֲשׂוֹתָן עַד עוֹלָם. וְכֵן הוּא אוֹמֵר חֻקַּת עוֹלָם לְדֹרֹתֵיכֶם. וְנֶאֱמַר (דברים ל יב) "לֹא בַשָּׁמַיִם הִיא". הָא לָמַדְתָּ שֶׁאֵין נָבִיא רַשַּׁאי לְחַדֵּשׁ דָּבָר מֵעַתָּה. לְפִיכָךְ אִם יַעֲמֹד אִישׁ בֵּין מִן הָאֻמּוֹת בֵּין מִיִּשְׂרָאֵל וְיַעֲשֶׂה אוֹת וּמוֹפֵת וְיֹאמַר שֶׁה' שְׁלָחוֹ לְהוֹסִיף מִצְוָה אוֹ לִגְרֹעַ מִצְוָה אוֹ לְפָרֵשׁ בְּמִצְוָה מִן הַמִּצְוֹת פֵּרוּשׁ שֶׁלֹּא שָׁמַעְנוּ מִמּשֶׁה. אוֹ שֶׁאָמַר שֶׁאוֹתָן הַמִּצְוֹת שֶׁנִּצְטַוּוּ בָּהֶן יִשְׂרָאֵל אֵינָן לְעוֹלָם וּלְדוֹרֵי דּוֹרוֹת אֶלָּא מִצְוֹת לְפִי זְמַן הָיוּ. הֲרֵי זֶה נְבִיא שֶׁקֶר שֶׁהֲרֵי בָּא לְהַכְחִישׁ נְבוּאָתוֹ שֶׁל משֶׁה. וּמִיתָתוֹ בְּחֶנֶק עַל שֶׁהֵזִיד לְדַבֵּר בְּשֵׁם ה' אֲשֶׁר לֹא צִוָּהוּ. שֶׁהוּא בָּרוּךְ שְׁמוֹ צִוָּה לְמשֶׁה שֶׁהַמִּצְוָה הַזֹּאת לָנוּ וּלְבָנֵינוּ עַד עוֹלָם וְ (במדבר כג יט) "לֹא אִישׁ אֵל וִיכַזֵּב":
כסף משנה
1.
It is clear and explicit in the Torah that it is [God's] commandment, remaining forever without change, addition, or diminishment, as [Deuteronomy 13:1] states: "All these matters which I command to you, you shall be careful to perform. You may not add to it or diminish from it," and [Deuteronomy 29:28] states: "What is revealed is for us and our children forever, to carry out all the words of this Torah." This teaches that we are commanded to fulfill all the Torah's directives forever.
It is also said: "It is an everlasting statute for all your generations," and [Deuteronomy 30:12] states: "It is not in the heavens." This teaches that a prophet can no longer add a new precept [to the Torah].
Therefore, if a person will arise, whether Jew or gentile, and perform a sign or wonder and say that God sent him to:
a) add a mitzvah,
b) withdraw a mitzvah
c) explain a mitzvah in a manner which differs from the tradition received from Moses, or
d) if he says that the mitzvot commanded to the Jews are not forever, but rather were given for a limited time,
he is a false prophet. He comes to deny the prophecy of Moses and should be executed by strangulation, because he dared to make statements in God's name which God never made.
God, blessed be His name, commanded Moses that this commandment is for us and our children forever, and, God is not man that He speak falsely.

הלכה ב
אִם כֵּן לָמָּה נֶאֱמַר בַּתּוֹרָה (דברים יח יח) "נָבִיא אָקִים לָהֶם מִקֶּרֶב אֲחֵיהֶם כָּמוֹךָ". לֹא לַעֲשׂוֹת דָּת הוּא בָּא אֶלָּא לְצַוּוֹת עַל דִּבְרֵי הַתּוֹרָה וּלְהַזְהִיר הָעָם שֶׁלֹּא יַעַבְרוּ עָלֶיהָ. כְּמוֹ שֶׁאָמַר הָאַחֲרוֹן שֶׁבָּהֶן (מלאכי ג כב) "זִכְרוּ תּוֹרַת משֶׁה עַבְדִּי". וְכֵן אִם צִוָּנוּ בְּדִבְרֵי הָרְשׁוּת כְּגוֹן לְכוּ לְמָקוֹם פְּלוֹנִי אוֹ אַל תֵּלְכוּ. עֲשׂוּ מִלְחָמָה הַיּוֹם אוֹ אַל תַּעֲשׂוּ. בְּנוּ חוֹמָה זוֹ אוֹ אַל תִּבְנוּהָ. מִצְוָה לִשְׁמֹעַ לוֹ. וְהָעוֹבֵר עַל דְּבָרָיו חַיָּב מִיתָה בִּידֵי שָׁמַיִם שֶׁנֶּאֱמַר (דברים יח יט) "וְהָיָה הָאִישׁ אֲשֶׁר לֹא יִשְׁמַע אֶל דְּבָרַי אֲשֶׁר יְדַבֵּר בִּשְׁמִי אָנֹכִי אֶדְרשׁ מֵעִמּוֹ":
כסף משנה
2.
If so, what is meant by the Torah's statement [Deuteronomy 18:18]: "I will appoint a prophet from among their brethren like you, and I
will place My words in his mouth and he will speak..."? He is not coming to establish a [new] faith, but rather to command the people [to fulfill] the precepts of the Torah and to warn against its transgression, as evidenced by the final prophet [Malachi], who proclaimed [Malachi 3:22], "Remember the Torah of Moses, My servant."
Also, a prophet may command us to do something which [is neither permitted nor forbidden by Torah law] - for example, "Go to such and such a place," "Do not go there," "Wage war today," or "Do not do so," "Build a wall," or "Do not build it."
[In these instances,] it is a mitzvah to listen to him. Anyone who violates his directives is liable for death at the hand of God, as [Deuteronomy 18:19] states: "And a person who will not heed My words which he speaks in My name, I will seek [retribution] from him."

הלכה ג
וְכֵן נָבִיא שֶׁעָבַר עַל דִּבְרֵי עַצְמוֹ וְהַכּוֹבֵשׁ נְבוּאָתוֹ חַיָּב מִיתָה בִּידֵי שָׁמַיִם וּבִשְׁלָשְׁתָּן נֶאֱמַר (דברים יח יט) "אָנֹכִי אֶדְרשׁ מֵעִמּוֹ". וְכֵן אִם יֹאמַר לָנוּ הַנָּבִיא שֶׁנּוֹדַע לָנוּ שֶׁהוּא נָבִיא לַעֲבֹר עַל אַחַת מִכָּל מִצְוֹת הָאֲמוּרוֹת בַּתּוֹרָה אוֹ עַל מִצְוֹת הַרְבֵּה בֵּין קַלּוֹת בֵּין חֲמוּרוֹת לְפִי שָׁעָה מִצְוָה לִשְׁמֹעַ לוֹ. וְכֵן לָמַדְנוּ מֵחֲכָמִים רִאשׁוֹנִים מִפִּי הַשְּׁמוּעָה בְּכָל אִם יֹאמַר לְךָ הַנָּבִיא עֲבֹר עַל דִּבְרֵי תּוֹרָה כְּאֵלִיָּהוּ בְּהַר הַכַּרְמֶל שְׁמַע לוֹ חוּץ מֵעֲבוֹדַת כּוֹכָבִים. וְהוּא שֶׁיִּהְיֶה הַדָּבָר לְפִי שָׁעָה. כְּגוֹן אֵלִיָּהוּ בְּהַר הַכַּרְמֶל שֶׁהִקְרִיב עוֹלָה בַּחוּץ וִירוּשָׁלַיִם נִבְחֶרֶת לְכָךְ וְהַמַּקְרִיב בַּחוּץ חַיָּב כָּרֵת. וּמִפְּנֵי שֶׁהוּא נָבִיא מִצְוָה לִשְׁמֹעַ לוֹ וְגַם בָּזֶה נֶאֱמַר (דברים יח טו) "אֵלָיו תִּשְׁמָעוּן". וְאִלּוּ שָׁאֲלוּ אֶת אֵלִיָּהוּ וְאָמְרוּ לוֹ הֵיאַךְ נַעֲקֹר מַה שֶּׁכָּתוּב בַּתּוֹרָה (דברים יב יג) "פֶּן תַּעֲלֶה עלֹתֶיךָ בְּכָל מָקוֹם". הָיָה אוֹמֵר לֹא נֶאֱמַר אֶלָּא הַמַּקְרִיב בַּחוּץ לְעוֹלָם חַיָּב כָּרֵת כְּמוֹ שֶׁצִּוָּה משֶׁה. אֲבָל אֲנִי אַקְרִיב הַיּוֹם בַּחוּץ בִּדְבַר ה' כְּדֵי לְהַכְחִישׁ נְבִיאֵי הַבַּעַל. וְעַל הַדֶּרֶךְ הַזֹּאת אִם צִוּוּ כָּל הַנְּבִיאִים לַעֲבֹר לְפִי שָׁעָה מִצְוָה לִשְׁמֹעַ לָהֶם. וְאִם אָמְרוּ שֶׁהַדָּבָר נֶעֱקַר לְעוֹלָם מִיתָתוֹ בְּחֶנֶק שֶׁהַתּוֹרָה אָמְרָה (דברים כט כח) "לָנוּ וּלְבָנֵינוּ עַד עוֹלָם":
כסף משנה
3.
Similarly, a prophet who violated his own prophetic instructions, and one who refrains from prophesying, are liable for death at the hand of God, since concerning the three of them, it is said, "I will seek [retribution] from him."
When a prophet - who has already proven himself to be a prophet - instructs us to violate one of the mitzvot of the Torah or many mitzvot, whether they be of a severe or light nature, for a limited amount of time, it is a mitzvah to listen to him.
The Sages of the early generation taught as part of the oral tradition: If a prophet tells you to violate the precepts of the Torah as Elijah did on Mount Carmel, listen to him with regard to all things except the worship of false gods. This applies when his command is temporary in nature.
For example, on Mount Carmel, Elijah offered a sacrifice outside [the Temple's premises], even though Jerusalem was chosen for such [service], and one who offers a sacrifice outside [the Temple's premises] is liable for karet. Since he was [already established as] a prophet, it was a mitzvah to listen to him. The commandment, "Listen to him," applies in these circumstances as well.
If they would have asked Elijah: How can we violate the Torah's command [Deuteronomy 12:13]: "[Be careful...] lest you offer your burnt offerings everywhere"?, he would have told them: We should not say anything, but anyone who offers a sacrifice outside [the Temple premises] is liable for karet, as Moses said. [The present instance,] however, [is an exception]. I am offering a sacrifice today outside [the Temple] at God's command in order to disprove the prophets of Ba'al.
Similarly, if any [other] prophet commands us to transgress for a limited time, it is a mitzvah to listen to him. If, however, he says that the mitzvah has been nullified forever, he is liable for execution by strangulation, for the Torah has told us: "[It is] for us and our children forever."

הלכה ד
וְכֵן אִם עָקַר דָּבָר מִדְּבָרִים שֶׁלָּמַדְנוּ מִפִּי הַשְּׁמוּעָה אוֹ שֶׁאָמַר בְּדִין מִדִּינֵי תּוֹרָה שֶׁה' צִוָּה לוֹ שֶׁהַדִּין כָּךְ הוּא וַהֲלָכָה כְּדִבְרֵי פְּלוֹנִי הֲרֵי זֶה נְבִיא הַשֶּׁקֶר וְיֵחָנֵק. אַף עַל פִּי שֶׁעָשָׂה אוֹת. שֶׁהֲרֵי בָּא לְהַכְחִישׁ הַתּוֹרָה שֶׁאָמְרָה (דברים ל יב) "לֹא בַשָּׁמַיִם הִיא". אֲבָל לְפִי שָׁעָה שׁוֹמְעִין לוֹ בַּכּל:
כסף משנה
4.
Similarly, if [a "prophet"] nullifies a concept which was transmitted by the oral tradition, or states with regard to one of the Torah's laws that God commanded him to render such and such a judgment, or that such and such is the law regarding a particular instance and the decision follows a certain opinion, he is a false prophet and should be [executed by] strangulation. [This applies] even if he performs a wonder, for he is coming to deny the Torah, which states: "It is not in the heavens."
If, however, [he states that] for a limited time [we should follow a particular course of behavior], he should be listened to with regard to all things.

הלכה ה
בַּמֶּה דְּבָרִים אֲמוּרִים בִּשְׁאָר מִצְוֹת. אֲבָל בַּעֲבוֹדַת כּוֹכָבִים אֵין שׁוֹמְעִין לוֹ וַאֲפִלּוּ לְפִי שָׁעָה. וַאֲפִלּוּ עָשָׂה אוֹתוֹת וּמוֹפְתִים גְּדוֹלִים וְאָמַר שֶׁה' צִוָּהוּ שֶׁתֵּעָבֵד עֲבוֹדַת כּוֹכָבִים הַיּוֹם בִּלְבַד אוֹ בְּשָׁעָה זוֹ בִּלְבַד הֲרֵי זֶה דִּבֵּר סָרָה עַל ה'. וְעַל זֶה צִוָּה הַכָּתוּב וְאָמַר (דברים יג ג) "וּבָא הָאוֹת וְהַמּוֹפֵת" (דברים יג ד) "לֹא תִּשְׁמַע אֶל דִּבְרֵי הַנָּבִיא הַהוּא" (דברים יג ו) "כִּי דִּבֵּר סָרָה עַל ה' אֱלֹהֵיכֶם". שֶׁהֲרֵי בָּא לְהַכְחִישׁ נְבוּאָתוֹ שֶׁל משֶׁה. וּלְפִיכָךְ נֵדַע בְּוַדַּאי שֶׁהוּא נְבִיא שֶׁקֶר וְכָל מַה שֶּׁעָשָׂה בְּלָט וְכִשּׁוּף עָשָׂה וְיֵחָנֵק:
כסף משנה
5.
When does the above apply? With regard to all other mitzvot. Regarding the worship of false gods, however, he should not be heeded, even for a limited time. Even if he performs great wonders and miracles and says that God commanded him to worship false gods only on this day or only during this hour, he is considered to have "spoken perversely against God."
Concerning this, the Torah has commanded [us, Deuteronomy 13:3-6]: "If a sign or miracle is performed... [and he tells you, `Let us serve other gods...'] Do not listen to the words of this prophet... for he has spoken perversely against God, your Lord." He is coming to deny the prophecy of Moses. Therefore, we may definitely conclude that he is a false prophet, and everything that he did was performed through sorcery and magic. [Hence,] he should be [executed by] strangulation.

מדע הלכות יסודי התורה פרק ט
Madda Yesodei haTorah Chapter 9