Shabbat 133a
שבת קל״ג א — ד"ה אָמַר אַבָּיֵי
Shabbat 133a:3
This daf contains a central discussion of pesik reisha and whether an inevitable result may be disregarded when it is not desired, a key principle in evaluating door-opening effects.
אָמַר אַבָּיֵי: לָא נִצְרְכָא אֶלָּא לְרַבִּי יְהוּדָה, דְּאָמַר דָּבָר שֶׁאֵין מִתְכַּוֵּין — אָסוּר. רָבָא אָמַר: אֲפִילּוּ תֵּימָא רַבִּי שִׁמְעוֹן, מוֹדֶה רַבִּי שִׁמְעוֹן בִּ״פְסִיק רֵישֵׁיהּ וְלָא יְמוּת״. וְאַבָּיֵי לֵית לֵיהּ הַאי סְבָרָא? וְהָא אַבָּיֵי וְרָבָא דְּאָמְרִי תַּרְוַיְיהוּ: מוֹדֶה רַבִּי שִׁמְעוֹן בִּ״פְסִיק רֵישֵׁיהּ וְלָא יְמוּת״! בָּתַר דְּשַׁמְעַהּ מֵרָבָא סַבְרַהּ. וְהָא לְמָה לִי קְרָא, דָּבָר שֶׁאֵין מִתְכַּוֵּין הוּא, וְדָבָר שֶׁאֵין מִתְכַּוֵּין — מוּתָּר! אָמַר אַבָּיֵי: לֹא נִצְרְכָה אֶלָּא לְרַבִּי יְהוּדָה דְּאָמַר: דָּבָר שֶׁאֵין מִתְכַּוֵּין — אָסוּר. וְרָבָא אָמַר אֲפִילּוּ תֵּימָא רַבִּי שִׁמְעוֹן, מוֹדֶה רַבִּי שִׁמְעוֹן בִּ״פְסִיק רֵישֵׁיהּ וְלָא יְמוּת״. וְאַבָּיֵי לֵית לֵיהּ הַאי סְבָרָא? וְהָא אַבָּיֵי וְרָבָא דְּאָמְרִי תַּרְוַויְיהוּ: מוֹדֶה רַבִּי שִׁמְעוֹן בִּ״פְסִיק רֵישֵׁיהּ וְלָא יְמוּת״! לְבָתַר דְּשַׁמְעֵיהּ מֵרָבָא סַבְרַהּ.
Abaye said: This derivation is only necessary according to the opinion of Rabbi Yehuda, who said that an unintentional act is prohibited. Rava said: Even if you say that it is according to the opinion of Rabbi Shimon, who holds that an unintentional act is permitted, as Rabbi Shimon concedes to Rabbi Yehuda in the case of: Cut off its head and will it not die, i.e., an unintentional act from which a prohibited labor ensued as an inevitable consequence. In that case, the one who performs the action cannot claim that the outcome was unintended. In the case of circumcising a leprous foreskin, the removal of leprosy is an inevitable consequence of the circumcision. The Gemara asks: And does Abaye not accept this reasoning? Wasn’t it Abaye and Rava who both say that Rabbi Shimon concedes to Rabbi Yehuda that in the case of: If you cut off its head will it not die? The Gemara answers: After Abaye heard this principle from Rava, he accepted it. The Gemara asks: Why do I need a verse to address this? It is an unintentional act, and an unintentional act is permitted. Abaye said: This derivation is only necessary according to the opinion of Rabbi Yehuda, who said that an unintentional act is prohibited. Rava said: Even if you say that it is according to the opinion of Rabbi Shimon, who holds that an unintentional act is permitted, as Rabbi Shimon concedes to Rabbi Yehuda in the case of: If you cut off its head will it not die? The Gemara asks: And does Abaye not accept this reasoning? Wasn’t it Abaye and Rava who both say that Rabbi Shimon concedes to Rabbi Yehuda that in the case of: Cut off its head and will it not die? The Gemara answers: After Abaye heard this principle from Rava, he accepted it.



