"And he shall take, he and his neighbor" (Exodus 12:4). Rabbi Akiva says: From where do you say that if a person wishes to make the Passover by himself he is permitted? Scripture says, "and he shall take, he." Rabbi Ishmael says: From where do you say that if a person wishes to enroll others upon his Passover he is permitted? Scripture says, "and he shall take, he and his neighbor." I might hear that this means his neighbor on his roof; or perhaps it means only his neighbor at his side? Scripture says, "the one near to his house"—Scripture speaks of the usual case. Rabbi Shimon ben Yochai says: his neighbor in any case. "According to the number [mikhsat]"—"number" means nothing other than a count, that he slaughter it for those enrolled upon it. But if he slaughtered it for those not enrolled upon it, I might hear that it is valid; Scripture says, "a man according to his eating you shall apportion"—Scripture repeated the matter to disqualify. Rabbi says: this is the Syrian tongue, like a person who says to his fellow, "Slaughter [kos] this lamb for me." We have found this regarding those not enrolled upon it; regarding those who will not eat it, from where do we know? Scripture says, "a man according to his eating you shall apportion"—it likens those who eat it to those enrolled upon it.
A Man and His Neighbor Counted by the Number Who Eat
Yalkut Shimoni on Torah 192:5
וְלָקַח הוּא וּשְׁכֵנוֹ, רַבִּי עֲקִיבָא אוֹמֵר, מִנַּיִן אַתָּה אוֹמֵר שֶׁאִם רוֹצֶה אָדָם לַעֲשׂוֹת פֶּסַח יְחִידִי הוּא רַשַּׁאי תַּלְמוּד לוֹמַר וְלָקַח הוּא, רַבִּי יִשְׁמָעֵאל אוֹמֵר מִנַּיִן אַתָּה אוֹמֵר שֶׁאִם רוֹצֶה אָדָם לְמַנּוֹת אֲחֵרִים עַל פִּסְחוֹ שֶׁהוּא רַשַּׁאי תַּלְמוּד לוֹמַר וְלָקַח הוּא וּשְׁכֵנוֹ. שׁוֹמֵעַ אֲנִי שְׁכֵנוֹ שֶׁבְּגַגּוֹ, אוֹ אֵינוֹ אֶלָּא שְׁכֵנוֹ שֶׁבְּצִדּוֹ תַּלְמוּד לוֹמַר הַקָּרֹב אֶל בֵּיתוֹ, דִבֵּר הַכָּתוּב בָּהוֹוֶה. רַבִּי שִׁמְעוֹן בֶּן יוֹחַאי אוֹמֵר, שְׁכֵנוֹ מִכָּל מָקוֹם. בְּמִכְסַת, אֵין מִכְסַת אֶלָּא מִנְיָן, שֶׁיִּשְׁחָטֶנּוּ לִמְנוּיָיו, אֲבָל אִם שְׁחָטוֹ שֶׁלֹּא לִמְנוּיָיו שׁוֹמֵעַ אֲנִי שֶׁיְּהֵא כָּשֵׁר, תַּלְמוּד לוֹמַר אִישׁ לְפִי אָכְלוֹ תָּכֹסּוּ שָׁנָּה עָלָיו הַכָּתוּב לִפְסֹל. רַבִּי אוֹמֵר לְשׁוֹן סוּרְסִי הוּא זֶה כְּאָדָם שֶׁאוֹמֵר לַחֲבֵרוֹ כּוֹס לִי טָלֶה זֶה אַשְׁכְּחַן שֶׁלֹּא לִמְנוּיָו, שֶׁלֹּא לְאוֹכְלָיו מִנָּלָן. אָמַר קְרָא, אִישׁ לְפִי אָכְלוֹ תָּכֹסּוּ, אִיתְקַשׁ אוֹכְלָיו לִמְנוּיָיו.