To not eat an unblemished firstborn [animal] outside of Jerusalem: That a priest not eat an unblemished firstborn [animal] outside of Jerusalem; and so too that a foreigner [non-priest] not eat from a firstborn in any place, as the commandment with it is that the priests — the servants of God — should eat it, from the reason that I wrote in the Order of Bo el Pharoah (Sefer HaChinukh 18). And about all of this is it written (Deuteronomy 12:17), “You may not eat in your gates, etc. and the firstborn of your cattle and your flocks.” And the language of Sifrei Devarim 72 (see [also] Makkot 17a) is “‘And the firstborn’ — this is the firstborn. And the verse only comes for a foreigner that ate the firstborn, whether before the sprinkling of the bloods or whether after the sprinkling, [to teach] that he transgresses a negative commandment.” And the intent is not that the verse does not teach anything except this matter (see Sefer HaMitzvot, Negative Commandments 144), but rather it is saying that this is [also] included in this negative prohibition. And it comes out that included in it are two matters that we mentioned: prevention of the foreigner from eating an unblemished firstborn in any place; and so too, prevention of the priest from eating it outside of Jerusalem. And both of the matters are predicated upon [it being] an unblemished firstborn. And there in the Order of Bo el Pharaoh, I wrote at what time and in what place the commandment of the firstborn is practiced and the disagreement among my teachers — God protect them — about the matter of the firstborn at this time. And there is no need to write at length about the reason for its being eaten in Jerusalem, as it is part of the consecrated foods — and as it is written in the Mishnah Zevachim 5:8, “The firstborn, the tithe and the Pesach-sacrifice-offering are low-level consecrated foods (kodashim kalim), etc.” — and I have already lavished my words in several places (Sefer HaChinukh 360) about the reason [for] the eating of consecrated foods in the holy place and their being eaten by the servants of God.
From the laws of the commandment — who is the foreigner regarding the eating of the firstborn, the blemishes that disqualify it, the time of its eating — it is all elucidated in Tractate Bekhorot. And a few of these laws are in other places in [the Order,] Kodashim. (See Mishneh Torah, Laws of Firstlings 1.) And a priest who transgresses it and eats a kazayit from an unblemished firstborn outside of Jerusalem, and so [too,] an Israelite in any place, is liable for lashes.
שֶׁלֹּא לֶאֱכֹל בְּכוֹר תָּמִים חוּץ לִירוּשָׁלַיִם – שֶׁלֹּא יֹאכַל הַכֹּהֵן בְּכוֹר תָּמִים חוּץ לִירוּשָׁלַיִם, וּכְמוֹ כֵן שֶׁלֹּא יֹאכַל זֵר מִן הַבְּכוֹר בְּשׁוּם מָקוֹם, כִּי הַמִּצְוָה בּוֹ שֶׁיֹּאכְלוּהוּ הַכֹּהֲנִים מְשָׁרְתֵי הַשֵּׁם, מִן הַטַּעַם שֶׁכָּתַבְתִּי בְּסֵדֶר בֹּא אֶל פַּרְעֹה (מצוה יח). וְעַל כָּל זֶה נֶאֱמַר (דברים יב יז) לֹא תוּכַל לֶאֱכֹל בִּשְׁעָרֶיךָ וְגוֹ'. וּבְכוֹרוֹת בְּקָרְךָ וְצֹאנֶךָ. וּלְשׁוֹן סִפְרֵי (כאן, ועיין מכות יז א) וּבְכוֹרוֹת זֶה הַבְּכוֹר, וְלֹא בָּא הַכָּתוּב אֶלָּא לְזָר שֶׁאָכַל בְּכוֹר, בֵּין לִפְנֵי זְרִיקַת דָּמִים בֵּין לְאַחַר זְרִיקָה שֶׁעוֹבֵר בְּלֹא תַּעֲשֶׂה. וְאֵין הַכַּוָּנָה שֶׁלֹּא יְלַמֵּד הַכָּתוּב זוּלָתִי עִנְיָן זֶה (עי' ספה"מ להרמב"ם ל"ת קמד), אֲבָל יֹאמַר שֶׁזֶּהוּ בִּכְלַל הַלָּאו הַזֶּה. וְנִמְצָא שֶׁכְּלוּלִים בּוֹ שְׁנֵי הָעִנְיָנִים שֶׁזָּכַרְנוּ, מְנִיעַת הַזָּר מִלֶּאֱכֹל בְּכוֹר תָּמִים בְּשׁוּם מָקוֹם, וּמְנִיעַת הַכֹּהֵן כְּמוֹ כֵן מִלֶּאֱכֹל אוֹתוֹ חוּץ לִירוּשָׁלַיִם, וּשְׁנֵי הָעִנְיָנִים תְּלוּיִם בִּבְכוֹר תָּמִים. וְשָׁם בְּסֵדֶר בֹּא אֶל פַּרְעֹה כָּתַבְתִּי מִצְוַת הַבְּכוֹר בְּאֵיזֶה זְמַן וּבְאֵי זֶה מָקוֹם נוֹהֶגֶת, וְחִלּוּק הַדֵּעוֹת לְרַבּוֹתַי יִשְׁמְרֵם אֵל בְּעִנְיַן הַבְּכוֹר בַּזְּמַן הַזֶּה. וּבְטַעַם הֱיוֹתוֹ נֶאֱכָל בִּירוּשָׁלַיִם אֵין צֹרֶךְ לְהַאֲרִיךְ, כִּי הוּא מִכְּלַל הַקֳּדָשִׁים, וּכְמוֹ שֶׁבָּא בַּמִּשְׁנָה בִּזְבָחִים פֶּרֶק ה' (מ"ח), הַבְּכוֹר וְהַמַּעֲשֵׂר וְהַפֶּסַח קָדָשִׁים קַלִּים וְכוּ'. וּכְבָר הֶעְתַּרְתִּי דְּבָרַי בְּכַמָּה מְקוֹמוֹת (מצוה שס) בְּטַעַם אֲכִילַת הַקֳּדָשִׁים בִּמְקוֹם הַקֹּדֶשׁ וֶאֱכֹל אוֹתָם מְשָׁרְתֵי הַשֵּׁם.
To not eat an unblemished firstborn [animal] outside of Jerusalem: That a priest not eat an unblemished firstborn [animal] outside of Jerusalem; and so too that a foreigner [non-priest] not eat from a firstborn in any place, as the commandment with it is that the priests — the servants of God — should eat it, from the reason that I wrote in the Order of Bo el Pharoah (Sefer HaChinukh 18). And about all of this is it written (Deuteronomy 12:17), “You may not eat in your gates, etc. and the firstborn of your cattle and your flocks.” And the language of Sifrei Devarim 72 (see [also] Makkot 17a) is “‘And the firstborn’ — this is the firstborn. And the verse only comes for a foreigner that ate the firstborn, whether before the sprinkling of the bloods or whether after the sprinkling, [to teach] that he transgresses a negative commandment.” And the intent is not that the verse does not teach anything except this matter (see Sefer HaMitzvot, Negative Commandments 144), but rather it is saying that this is [also] included in this negative prohibition. And it comes out that included in it are two matters that we mentioned: prevention of the foreigner from eating an unblemished firstborn in any place; and so too, prevention of the priest from eating it outside of Jerusalem. And both of the matters are predicated upon [it being] an unblemished firstborn. And there in the Order of Bo el Pharaoh, I wrote at what time and in what place the commandment of the firstborn is practiced and the disagreement among my teachers — God protect them — about the matter of the firstborn at this time. And there is no need to write at length about the reason for its being eaten in Jerusalem, as it is part of the consecrated foods — and as it is written in the Mishnah Zevachim 5:8, “The firstborn, the tithe and the Pesach-sacrifice-offering are low-level consecrated foods (kodashim kalim), etc.” — and I have already lavished my words in several places (Sefer HaChinukh 360) about the reason [for] the eating of consecrated foods in the holy place and their being eaten by the servants of God.
מִדִּינֵי הַמִּצְוָה. מִי הוּא הַזָּר אֵצֶל אֲכִילַת הַבְּכוֹר, וְהַמּוּמִין הַפּוֹסְלִין בּוֹ, וּזְמַן אֲכִילָתוֹ הַכֹּל מְבֹאָר בְּמַסֶּכֶת בְּכוֹרוֹת וּבִמְקוֹמוֹת אֲחֵרִים מִקָּדָשִׁים קְצָת מִדִּינִין אֵלּוּ [הלכות בכורות פ"א]. וְכֹהֵן הָעוֹבֵר עַל זֶה וְאָכַל כַּזַּיִת מִבְּכוֹר תָּמִים חוּץ לִירוּשָׁלַיִם, וְכֵן יִשְׂרָאֵל בְּכָל מָקוֹם חַיָּב מַלְקוּת.
From the laws of the commandment — who is the foreigner regarding the eating of the firstborn, the blemishes that disqualify it, the time of its eating — it is all elucidated in Tractate Bekhorot. And a few of these laws are in other places in [the Order,] Kodashim. (See Mishneh Torah, Laws of Firstlings 1.) And a priest who transgresses it and eats a kazayit from an unblemished firstborn outside of Jerusalem, and so [too,] an Israelite in any place, is liable for lashes.