Mishnayos Pesachim Perek 9 Mishnah 9

With regard to a group whose Paschal lamb was lost, and they said to one member of the group: Go and search for our Paschal lamb, and when you find it, slaughter it on our behalf; and he went and found the missing offering and slaughtered it on behalf of the entire group, but in the meantime they took a different animal and slaughtered it as a Paschal lamb, the halakha is as follows: If his Paschal lamb was slaughtered first, he eats from his offering, as he is considered to be registered specifically for that offering, and they eat with him from his offering, because he included them in his offering and it belongs to the entire group. The second animal does not have any registrants and is therefore burned. And if theirs was slaughtered first, they eat from theirs because they withdrew from the original offering through the act of slaughtering a replacement, and he eats from his because he was not registered for the replacement offering sacrificed by the remainder of his group. And if it is not known which of the offerings was slaughtered first, or if both the group and the individual slaughtered them together, he eats from his and they do not eat with him in case theirs was slaughtered first, and theirs must be taken out to the place designated for burning. The offering slaughtered by the group may not be eaten due to the concern that it was slaughtered second and the members of the group would therefore have been included in the first offering. However, they are exempt from performing the offering of the Paschal lamb on the second Pesaḥ, because they were included in the slaughter of whichever animal was slaughtered first. It is only due to external circumstances that they cannot complete the mitzva by eating the Paschal lamb, and this does not prevent them from fulfilling their obligation. A somewhat different case of a lost Paschal lamb would occur if the group had sent one member as an agent to search for the lost animal, and the agent said to the other members of the group before he left: If I am late, go and slaughter a Paschal lamb for me. He then went and found the lost Paschal lamb and slaughtered it, and they took another animal and slaughtered it as a Paschal lamb. In that case, if theirs was slaughtered first, they eat from theirs and he eats with them, because he requested to be included in their offering and they registered him for their Paschal lamb. And if his was slaughtered first, he eats from his and they eat from theirs, because the fact that they slaughtered a different animal indicates that they have withdrawn from the original offering. And if it is not known which of the animals was slaughtered first, or if both the group and the individual slaughtered them together, they eat from theirs because they definitely withdrew from the original offering by slaughtering a different one, and he does not eat with them because he also intended to be included in the animal he slaughtered and it is not clear which was slaughtered first. Therefore, his must be taken out to the place designated for burning; and he is exempt from performing the sacrifice of the Paschal lamb on the second Pesaḥ. If he said to them that if he is delayed they should include him in their Paschal lamb, and they said to him that if he finds the original offering he should slaughter it on their behalf, all of them eat from the first sacrifice that was slaughtered. And if it is not known which of them was slaughtered first, both of them must be taken out to the place designated for burning, and the entire group is exempt from participating in the Paschal lamb on the second Pesaḥ. If he did not say anything to them and they did not say anything to him, meaning that neither side granted the other authority to slaughter a Paschal lamb on its behalf, they are not responsible for each other, and the members of the group eat their Paschal lamb while the individual sent to find the lost animal eats from his own offering. The reason for this is that the individual is registered only for the original offering, while the other members of the group withdrew from that lost offering by sacrificing a different Paschal lamb.

חֲבוּרָה שֶׁאָבַד פִּסְחָהּ, וְאָמְרָה לְאֶחָד, צֵא וּבַקֵּשׁ וּשְׁחֹט עָלֵינוּ, וְהָלַךְ וּמָצָא וְשָׁחַט, וְהֵם לָקְחוּ וְשָׁחֲטוּ, אִם שֶׁלּוֹ נִשְׁחַט רִאשׁוֹן, הוּא אוֹכֵל מִשֶּׁלּוֹ, וְהֵם אוֹכְלִים עִמּוֹ מִשֶּׁלּוֹ, וְאִם שֶׁלָּהֶן נִשְׁחַט רִאשׁוֹן, הֵם אוֹכְלִין מִשֶּׁלָּהֶן, וְהוּא אוֹכֵל מִשֶּׁלּוֹ. וְאִם אֵינוֹ יָדוּעַ אֵיזֶה מֵהֶן נִשְׁחַט רִאשׁוֹן, אוֹ שֶׁשָּׁחֲטוּ שְׁנֵיהֶן כְּאֶחָד, הוּא אוֹכֵל מִשֶּׁלּוֹ, וְהֵם אֵינָם אוֹכְלִים עִמּוֹ, וְשֶׁלָּהֶן יֵצֵא לְבֵית הַשְּׂרֵפָה, וּפְטוּרִין מִלַּעֲשׂוֹת פֶּסַח שֵׁנִי. אָמַר לָהֶן, אִם אֵחַרְתִּי, צְאוּ וְשַׁחֲטוּ עָלָי. הָלַךְ וּמְצָאוֹ, וְשָׁחַט, וְהֵן לָקְחוּ וְשָׁחֲטוּ, אִם שֶׁלָּהֶן נִשְׁחַט רִאשׁוֹן, הֵן אוֹכְלִין מִשֶּׁלָּהֶן, וְהוּא אוֹכֵל עִמָּהֶן. וְאִם שֶׁלּוֹ נִשְׁחַט רִאשׁוֹן, הוּא אוֹכֵל מִשֶּׁלּוֹ, וְהֵן אוֹכְלִין מִשֶּׁלָּהֶן. וְאִם אֵינוֹ יָדוּעַ אֵיזֶה מֵהֶם נִשְׁחַט רִאשׁוֹן, אוֹ שֶׁשָּׁחֲטוּ שְׁנֵיהֶם כְּאֶחָד, הֵן אוֹכְלִין מִשֶּׁלָּהֶן, וְהוּא אֵינוֹ אוֹכֵל עִמָּהֶן, וְשֶׁלּוֹ יֵצֵא לְבֵית הַשְּׂרֵפָה, וּפָטוּר מִלַּעֲשׂוֹת פֶּסַח שֵׁנִי. אָמַר לָהֶן וְאָמְרוּ לוֹ, אוֹכְלִין כֻּלָּם מִן הָרִאשׁוֹן. וְאִם אֵין יָדוּעַ אֵיזֶה מֵהֶן נִשְׁחַט רִאשׁוֹן, שְׁנֵיהֶם יוֹצְאִין לְבֵית הַשְּׂרֵפָה. לֹא אָמַר לָהֶן וְלֹא אָמְרוּ לוֹ, אֵינָן אַחֲרָאִין זֶה לָזֶה: