מִצְוַת מַעֲשֵׂה הָאָשָׁם – שֶׁנִּצְטַוִּינוּ שֶׁיַּעֲשׂוּ הַכֹּהֲנִים מְלֶאכֶת קָרְבַּן הָאָשָׁם עַל הָעִנְיָן הַנִּזְכָּר בַּכָּתוּב, שֶׁנֶּאֱמַר (ויקרא ז א) וְזֹאת תּוֹרַת הָאָשָׁם וְגוֹ', כְּמוֹ שֶׁכָּתוּב בַּפָּרָשָׁה. הֲלֹא אָמַרְתִּי לְךָ (מצוה קלח), שֶׁאֵין לָנוּ לִכְתֹּב שֹׁרֶשׁ בִּמְלָאכוֹת אֵלּוּ לְפִי שֶׁהֵן כְּעֵין פְּרָטֵי הַקָּרְבָּן, וְאֵין לְחַזֵּר אַחַר טַעְמָן כִּי סְתוּמִין הַדְּבָרִים וַחֲתוּמִים. The commandment of the procedure of the guilt-offering: That we were commanded that the priests execute the process of the guilt-offering according to the manner described in Scripture, as it is stated (Leviticus 7:1), “This is the law of the guilt-offering, etc.,” as it is written in the passage. Did I not tell you (Sefer HaChinukh 138) that we should not write the root in these processes, since they are similar to the details of the sacrifices — and one should not seek after their reasons, as they are things that are blocked and sealed.
דִּינֵי הָאָשָׁם זָכַרְנוּ קְצָתָם לְמַעְלָה בְּפָרָשַׁת וַיִּקְרָא (מצוה קכט), וַעֲדַיִן נוֹדִיעַ שֶׁהָאָשָׁם אֵינוֹ בָּא לְעוֹלָם אֶלָּא מִזִּכְרֵי כְּבָשִׂים בִּלְבַד. יֵשׁ אָשָׁם בָּא מִגְּדוֹלֵי הַמִּין, וְיֵשׁ מִן הַקְּטַנִּים. מַעֲשֵׂהוּ בִּשְׁחִיטָה וּזְרִיקָה וּמְלִיחָה וְהָאֵמוּרִין וְהַתְּנוּפָה בַּאֲשָׁמוֹת שָׁוֶה, חוּץ מֵאֲשַׁם מְצֹרָע, שֶׁיֵּשׁ שִׁנּוּי קְצָת בְּקַבָּלַת דָּמוֹ. וְיֶתֶר פְּרָטֵי הַמִּצְוָה מְבֹאָרִים בִּזְבָחִים. I have mentioned a few of the laws of the guilt-offering in Parashat Vayikra (Sefer HaChinukh 129). But we shall still inform that a sin-offering always only comes from male sheep — there are some guilt-offerings that come from the large animals of the species and there are some from the small ones. Its procedure in slaughtering, sprinkling, salting the entrails and the waving is the same in [all of] the guilt-offerings — except for the guilt-offering of the metsora, which has a little difference regarding the reception of its blood. And the rest of the details of the commandment are in Zevachim.
וְנוֹהֶגֶת בִּזְמַן הַבַּיִת בְּזִכְרֵי כְּהֻנָּה. וְכֹהֵן הָעוֹבֵר עָלֶיהָ וְלֹא הִקְרִיב הָאָשָׁם כְּמִשְׁפָּטוֹ, בִּטֵּל עֲשֵׂה. And it is practiced at the time of the [Temple] by the males of the priesthood. And a priest that transgresses it and does not offer the guilt-offering according to its statute has violated this positive commandment.