Beitzah 12b
ביצה י״ב ב — ד"ה אֲמַר לֵיהּ
Beitzah 12b:2
Rabbi Yohanan rejects a baraita prohibiting kindling and cooking on a Festival as not consistent with halakha, explaining that according to Beit Hillel's principle—that if an action is permitted for food preparation purposes on a Festival it is also permitted for other purposes—kindling cannot be included among prohibited labors on a Festival.
אֲמַר לֵיהּ: פּוֹק תְּנִי לְבָרָא, הַבְעָרָה וּבִשּׁוּל אֵינָהּ מִשְׁנָה. וְאִם תִּמְצָא לוֹמַר מִשְׁנָה — בֵּית שַׁמַּאי הִיא, דְּאָמְרִי: לָא אָמְרִינַן מִתּוֹךְ שֶׁהוּתְּרָה הוֹצָאָה לְצוֹרֶךְ הוּתְּרָה נָמֵי שֶׁלֹּא לְצוֹרֶךְ. הָכָא נָמֵי, לָא אָמְרִינַן: מִתּוֹךְ שֶׁהוּתְּרָה הַבְעָרָה לְצוֹרֶךְ, הוּתְּרָה נָמֵי שֶׁלֹּא לְצוֹרֶךְ. דְּאִי בֵּית הִלֵּל — כֵּיוָן דְּאָמְרִי מִתּוֹךְ שֶׁהוּתְּרָה הוֹצָאָה לְצוֹרֶךְ הוּתְּרָה נָמֵי שֶׁלֹּא לְצוֹרֶךְ, הָכָא נָמֵי: מִתּוֹךְ שֶׁהוּתְּרָה הַבְעָרָה לְצוֹרֶךְ — הוּתְּרָה נָמֵי שֶׁלֹּא לְצוֹרֶךְ.
Rabbi Yoḥanan said to that tanna: Leave and teach it outside, i.e., this baraita is not fit for discussion in the study hall. The opinion that there is a prohibition against kindling and cooking on a Festival is not a mishna worthy of serious consideration. And if you say that it is a mishna rather than an error, this statement is still not in accordance with the halakha, as it is following the opinion of Beit Shammai, who say: We do not say: Since carrying out was permitted on a Festival for the purposes of food preparation, it was also permitted when performed not for these purposes. Here, too, we do not say: Since kindling was permitted on a Festival for the purposes of food preparation, it was also permitted when performed not for these purposes. The Gemara explains why the baraita cannot be attributed to Beit Hillel. If one were to suggest that this baraita follows the opinion of Beit Hillel, this cannot be the case, as they say: Since carrying out was permitted for the purposes of food preparation, it was also permitted when performed not for these purposes. Here, too, since kindling was permitted for the purposes of food preparation, it was also permitted when performed not for these purposes. Therefore, according to the opinion of Beit Hillel, kindling cannot be included amongst those prohibitions for which one is liable on a Festival.

