This collection of almost fifty Mishnayos mentioning Pesach and related topics (other than the MIshnayos in Mesechtas Pesachim) will form the basis of a study on the pervasiveness of the holiday of Pesach in the national consciousness and the Chachomim's integration of Pesach within the larger Halachik corpus.
More specifically, Mesechtas Pesachim focuses on the specific and practical application of the Mitzvos of Pesach. The ridding of Chametz, Matzoh, Korban Pesach and Seder Night. (A collection of source sheets related to these topics can be found here: https://www.sefaria.org/collections/pesach). The following Mishnayos, however, approach the holiday from different perspectives.
First, as the start of the spring season, Chodesh H'Aviv, in addition to having agricultural meaning, it was also viewed as a natural inflection point of the year.
Second, while Mishnayos Pesachim focuses on the the unique aspects of the Korban Pesach, there are numerous Mishnayos discussing the Korban Pesach within the context of other Korbonos.
Third, a number of Mishnayos focus on the prohibitions of Chametz and other items on Pesach.
Finally, many Mishnayos discuss the applicability of other Halochos to various aspects of Pesach.
(א) כָּל הַזְּבָחִים שֶׁנִזְבְּחוּ שֶׁלֹּא לִשְׁמָן, כְּשֵׁרִים, אֶלָּא שֶׁלֹּא עָלוּ לַבְּעָלִים לְשֵׁם חוֹבָה. חוּץ מִן הַפֶּסַח וּמִן הַחַטָּאת. הַפֶּסַח בִּזְמַנּוֹ, וְהַחַטָּאת, בְּכָל זְמָן. רַבִּי אֱלִיעֶזֶר אוֹמֵר, אַף הָאָשָׁם. הַפֶּסַח בִּזְמַנּוֹ, וְהַחַטָּאת וְהָאָשָׁם, בְּכָל זְמָן. אָמַר רַבִּי אֱלִיעֶזֶר, הַחַטָּאת בָּאָה עַל חֵטְא, וְהָאָשָׁם בָּא עַל חֵטְא. מַה חַטָּאת פְּסוּלָה שֶׁלֹּא לִשְׁמָהּ, אַף הָאָשָׁם פָּסוּל שֶׁלֹּא לִשְׁמוֹ:
(ב) יוֹסֵי בֶן חוֹנִי אוֹמֵר, הַנִּשְׁחָטִים לְשֵׁם פֶּסַח וּלְשֵׁם חַטָּאת, פְּסוּלִים. שִׁמְעוֹן אֲחִי עֲזַרְיָה אוֹמֵר, שְׁחָטָן לְשֵׁם גָּבוֹהַּ מֵהֶם, כְּשֵׁרִין. לְשֵׁם נָמוּךְ מֵהֶם, פְּסוּלִים. כֵּיצַד. קָדְשֵׁי קָדָשִׁים שֶׁשְּׁחָטָן לְשֵׁם קָדָשִׁים קַלִּים, פְּסוּלִין. קָדָשִׁים קַלִּים שֶׁשְּׁחָטָן לְשֵׁם קָדְשֵׁי קָדָשִׁים, כְּשֵׁרִין. הַבְּכוֹר וְהַמַּעֲשֵׂר שֶׁשְּׁחָטָן לְשֵׁם שְׁלָמִים, כְּשֵׁרִין. וּשְׁלָמִים שֶׁשְּׁחָטָן לְשֵׁם בְּכוֹר, לְשֵׁם מַעֲשֵׂר, פְּסוּלִין:
(ג) הַפֶּסַח שֶׁשְּׁחָטוֹ בְשַׁחֲרִית בְּאַרְבָּעָה עָשָׂר שֶׁלֹּא לִשְׁמוֹ, רַבִּי יְהוֹשֻׁעַ מַכְשִׁיר, כְּאִלּוּ נִשְׁחַט בִּשְׁלשָׁה עָשָׂר. בֶּן בְּתֵירָא פּוֹסֵל, כְּאִלּוּ נִשְׁחַט בֵּין הָעַרְבָּיִם. אָמַר שִׁמְעוֹן בֶּן עַזַּאי, מְקֻבָּל אֲנִי מִפִּי שִׁבְעִים וּשְׁנַיִם זָקֵן, בְּיוֹם שֶׁהוֹשִׁיבוּ רַבִּי אֶלְעָזָר בֶּן עֲזַרְיָה בַיְשִׁיבָה, שֶׁכָּל הַזְּבָחִים הַנֶּאֱכָלִים שֶׁנִּזְבְּחוּ שֶׁלֹּא לִשְׁמָן, כְּשֵׁרִים, אֶלָּא שֶׁלֹּא עָלוּ לַבְּעָלִים מִשּׁוּם חוֹבָה, חוּץ מִן הַפֶּסַח וּמִן הַחַטָּאת. וְלֹא הוֹסִיף בֶּן עַזַּאי אֶלָּא הָעוֹלָה, וְלֹא הוֹדוּ לוֹ חֲכָמִים:
(ד) הַפֶּסַח וְהַחַטָּאת שֶׁשְּׁחָטָן שֶׁלֹּא לִשְׁמָן, קִבֵּל, וְהִלֵּךְ, וְזָרַק, שֶׁלֹּא לִשְׁמָן, אוֹ לִשְׁמָן וְשֶׁלֹּא לִשְׁמָן, אוֹ שֶׁלֹּא לִשְׁמָן וְלִשְׁמָן, פְּסוּלִים. כֵּיצַד לִשְׁמָן וְשֶׁלֹּא לִשְׁמָן, לְשֵׁם פֶּסַח וּלְשֵׁם שְׁלָמִים. שֶׁלֹּא לִשְׁמָן וְלִשְׁמָן, לְשֵׁם שְׁלָמִים וּלְשֵׁם הַפֶּסַח. שֶׁהַזֶּבַח נִפְסָל בְּאַרְבָּעָה דְבָרִים, בַּשְּׁחִיטָה וּבַקִּבּוּל וּבַהִלּוּךְ וּבַזְּרִיקָה. רַבִּי שִׁמְעוֹן מַכְשִׁיר בְּהִלּוּךְ, שֶׁהָיָה רַבִּי שִׁמְעוֹן אוֹמֵר, אִי אֶפְשָׁר שֶׁלֹּא בִשְׁחִיטָה וְשֶׁלֹּא בְקַבָּלָה וְשֶׁלֹּא בִזְרִיקָה, אֲבָל אֶפְשָׁר שֶׁלֹּא בְהִלּוּךְ, שׁוֹחֵט בְּצַד הַמִּזְבֵּחַ וְזוֹרֵק. רַבִּי אֱלִיעֶזֶר אוֹמֵר, הַמְהַלֵּךְ בִּמְקוֹם שֶׁהוּא צָרִיךְ לְהַלֵּךְ, הַמַּחֲשָׁבָה פוֹסֶלֶת. וּבִמְקוֹם שֶׁאֵין צָרִיךְ לְהַלֵּךְ, אֵין הַמַּחֲשָׁבָה פוֹסָלֶת:
(1) All slaughtered offerings that were slaughtered not for their own sake, i.e., during the slaughtering the slaughterer’s intent was to sacrifice a different offering, are fit, and one may continue their sacrificial rites and partake of their meat where that applies. But these offerings did not satisfy the obligation of the owner, who is therefore required to bring another offering. This is the halakha with regard to all offerings except for the Paschal offering and the sin offering. In those cases, if the owner sacrificed them not for their own sake, they are unfit. But there is a difference between the two exceptions. The Paschal offering is unfit only when sacrificed not for its sake at its appointed time, on the fourteenth day of Nisan after noon, while the sin offering is unfit any time that it is sacrificed not for its sake. Rabbi Eliezer says: The guilt offering too is unfit when sacrificed not for its sake. According to his opinion, the correct reading of the mishna is: The Paschal offering is unfit only at its appointed time, while the sin offering and the guilt offering are unfit at all times. Rabbi Eliezer said in explanation: The sin offering is brought for performance of a transgression and the guilt offering is brought for performance of a transgression. Just as a sin offering is unfit when sacrificed not for its sake, so too, the guilt offering is unfit when sacrificed not for its sake.
(2) Yosei ben Ḥoni says: Not only are the Paschal offering and the sin offering unfit when slaughtered not for their sake, but also other offerings that are slaughtered for the sake of a Paschal offering and for the sake of a sin offering are unfit. Shimon, brother of Azarya, says that this is the distinction: With regard to all offerings, if one slaughtered them for the sake of an offering whose level of sanctity is greater than theirs, they are fit; if one slaughtered them for the sake of an offering whose level of sanctity is less than theirs, they are unfit. How so? Offerings of the most sacred order, e.g., sin offerings and burnt offerings, that one slaughtered for the sake of offerings of lesser sanctity, e.g., peace offerings, are unfit. Offerings of lesser sanctity that one slaughtered for the sake of offerings of the most sacred order are fit. Likewise, there is a distinction between different offerings of lesser sanctity. The firstborn animal and the animal tithe that one slaughtered for the sake of a peace offering are fit, as the sanctity of peace offerings is greater. Peace offerings that one slaughtered for the sake of a firstborn animal or for the sake of an animal tithe are unfit.
(3) With regard to the Paschal offering that one slaughtered on the morning of the fourteenth of Nisan, the day when the Paschal offering should be slaughtered in the afternoon, if he did so not for its sake, Rabbi Yehoshua deems it fit as though it were slaughtered on the thirteenth of Nisan. An animal consecrated as a Paschal offering that was slaughtered not at its designated time for the sake of a different offering is fit for sacrifice as a peace offering. Ben Beteira deems it unfit as though it were slaughtered in the afternoon of the fourteenth. Shimon ben Azzai said: I received a tradition from seventy-two elders, as the Sanhedrin deliberated and decided on the day that they installed Rabbi Elazar ben Azarya at the head of the yeshiva and ruled that all the slaughtered offerings that are eaten that were slaughtered not for their sake are fit, but these offerings did not satisfy the obligation of the owner, except for the Paschal offering and the sin offering. Based on that version, ben Azzai added to the halakha cited in the first mishna only the burnt offering, which is not eaten, and the Rabbis disagreed and did not concede to him.
(4) With regard to the Paschal offering and the sin offering, where one slaughtered them not for their sake, or where he collected their blood in a vessel, conveyed this blood to the altar, or sprinkled this blood on the altar not for their sake, or where he performed one of these sacrificial rites for their sake and not for their sake, or not for their sake and for their sake, in all these cases the offerings are unfit. How are these rites performed for their sake and not for their sake? In a case where one slaughtered the Paschal offering for the sake of a Paschal offering and for the sake of a peace offering. How are these rites performed not for their sake and for their sake? In a case where one slaughtered the Paschal offering for the sake of a peace offering and for the sake of a Paschal offering. The offering is unfit because a slaughtered offering is disqualified due to prohibited intent in four matters: In the performance of the sacrificial rites of slaughtering the animal, in collecting the blood, in conveying the blood, and in sprinkling the blood. Rabbi Shimon deems the offering fit if the prohibited intent was during the rite of conveying the blood, as he would say: It is impossible to sacrifice an offering without slaughtering the animal, or without collection of the blood, or without sprinkling the blood, but it is possible to sacrifice an offering without conveying the blood to the altar. How so? If one slaughters the animal alongside the altar and sprinkles the blood, the blood does not need to be conveyed. Therefore, the rite of conveying the blood is not significant enough to cause the offering to be disqualified due to prohibited intent while performing it. Rabbi Eliezer says: With regard to one who conveys the blood in a situation where he is required to convey it, prohibited intent while conveying it disqualifies the offering. If he conveys the blood in a situation where he is not required to convey it, prohibited intent while conveying it does not disqualify the offering.