דברים ט״ו:י״ט-כ״ג

כל הבכור, תקדיש. וּבְמָקוֹם אַחֵר (ויקרא כ"ז) הוּא אוֹמֵר "לֹא יַקְדִּישׁ אִישׁ אֹתוֹ", הָא כֵיצַד? אֵינוֹ מַקְדִּישׁוֹ לְקָרְבָּן אַחֵר; וְכָאן לִמֵּד שֶׁמִּצְוָה לוֹמַר הֲרֵי אַתָּה קָדוֹשׁ לִבְכוֹרָה. דָּ"אַ — אִי אֶפְשָׁר לוֹמַר "תַּקְדִּישׁ", שֶׁכְּבָר נֶאֱמַר "לֹא יַקְדִּישׁ", וְאִי אֶפְשָׁר לוֹמַר "לֹא יַקְדִּישׁ", שֶׁהֲרֵי כְבָר נֶאֱמַר "תַּקְדִּישׁ", הָא כֵיצַד? מַקְדִּישׁוֹ אַתָּה הֶקְדֵּשׁ עִלּוּי וְנוֹתֵן לַהֶקְדֵּשׁ כְּפִי טוֹבַת הֲנָאָה שֶׁבּוֹ (ערכין כ"ט):

Every firstborn . . . you must consecrate. Elsewhere it is said that one should not consecrate him. How is this resolved? He may not consecrate him as a different sacrifice. Here, however, it teaches that it is a mitzvah to declare ‘You are hereby consecrated as a firstborn.’ Another interpretation. One cannot say “You must consecrate”! since it has already been said. “Do not consecrate”! And one cannot say “Do not consecrate”! since it has already been said, “You must consecrate”! How is this resolved? You may consecrate it whereby its monetary value becomes sacred, then donate, to the sacred hekdesh domain, the value of its beneficiary payment.

לא תעבד בבכור שורך ולא תגז וגו'. אַף הַחִלּוּף לָמְדוּ רַבּוֹתֵינוּ שֶׁאָסוּר, אֶלָּא שֶׁדִּבֵּר הַכָּתוּב בַּהוֹוֶה (בכורות כ"ה):

You may not work with your first-born ox, or shear, etc. The converse, as well, is prohibited by Rabbinic derivation, but Scripture depicts what is commonly practiced.

לפני ה' אלהיך תאכלנו. לַכֹּהֵן הוּא אוֹמֵר, שֶׁכְּבָר מָצִינוּ שֶׁהוּא מִמַּתְּנוֹת כְּהֻנָּה אֶחָד תָּם וְאֶחָד בַּעַל מוּם, שֶׁנֶּאֱמַר (במדבר י"ח) וּבְשָׂרָם יִהְיֶה לָּךְ וְגוֹ' (בכ' כ"ח):

Before Adonoy your God, you must eat it. This is addressed to the kohein, as we already find that this is one of the priestly gifts, whether sound or blemished, as it is said, “Their flesh shall be yours, etc.”

שנה בשנה. מִכָּאן שֶׁאֵין מַשְׁהִין אוֹתוֹ יוֹתֵר עַל שְׁנָתוֹ; יָכוֹל יְהֵא פָּסוּל מִשֶּׁעָבְרָה שְׁנָתוֹ, כְּבָר הֻקַּשׁ לְמַעֲשֵׂר, שֶׁנֶּאֱמַר (דברים י"ד) וְאָכַלְתָּ לִפְנֵי ה' אֱלֹהֶיךָ מַעְשַׂר דְּגָנְךָ תִּירֹשְׁךָ וְיִצְהָרֶךָ וּבְכֹרֹת בְּקָרְךָ וְצֹאנֶךָ, מַה מַּעֲשֵׂר שֵׁנִי אֵינוֹ נִפְסָל מִשָּׁנָה לַחֲבֶרְתָּהּ אַף בְּכוֹר אֵינוֹ נִפְסָל, אֶלָּא שֶׁמִּצְוָה תּוֹךְ שְׁנָתוֹ (בכ' כ"ז):

Each year. This teaches that it should not be detained for more than a year. Perhaps it becomes disqualified once the year had passed? It has already been compared to the tithe, as it is said, “You must eat, before Adonoy your God, etc., the tithe of your grain, wine, and oil, and the first-born of your cattle and flocks.” Just as the second tithe is not disqualified from one year to the next, so is the first-born not disqualified. Rather, it is a mitzvah within the year.

שנה בשנה. אִם שְׁחָטוֹ בְּסוֹף שְׁנָתוֹ אוֹכְלוֹ אוֹתוֹ הַיּוֹם וְיוֹם אֶחָד מִשָּׁנָה אַחֶרֶת, לִמֵּד שֶׁנֶּאֱכָל לִשְׁנֵי יָמִים וְלַיְלָה אֶחָד (שם):

Each year [lit. year by year]. If it was slaughtered at the end of the year, it may be eaten that day, and another day into the following year. This teaches that it may be eaten for two days and a night.

מום. כְּלָל:

A blemish. This is a general statement.

פסח או עור. פְּרָט:

If it is crippled or blind. This is specific.

כל מום רע. חָזַר וְכָלַל — מַה הַפְּרָט מְפֹרָשׁ מוּם הַגָּלוּי וְאֵינוֹ חוֹזֵר, אַף כָּל מוּם שֶׁבַּגָּלוּי וְאֵינוֹ חוֹזֵר (שם ל"ז):

Any severe blemish. This returns to the general. Just as the specific statement refers explicitly to a visible permanent blemish, so must every disqualifying blemish be visible and permanent.

רק את דמו לא תאכל. שֶׁלֹּא תֹאמַר הוֹאִיל וְכֻלּוֹ הֶתֵּר הַבָּא מִכְּלַל אִסּוּר הוּא, שֶׁהֲרֵי קָדוֹשׁ וְנִשְׁחָט בַּחוּץ בְּלֹא פִדְיוֹן וְנֶאֱכָל, יָכוֹל יְהֵא אַף הַדָּם מֻתָּר, תַּלְמוּד לוֹמַר רק את דמו לא תאכל:

Only, do not eat its blood. In order that you do not say that, as the entire animal is permitted by exemption from a generally prohibited category — since it is sacred, yet may be slaughtered outside the sanctuary without redemption and eaten — then perhaps even its blood is permitted. The Torah therefore teaches “Only do not eat its blood.”