Shevuos 2:3 - 2:4

The first part of the mishna discussed one who became ritually impure before entering the Temple. The mishna proceeds to consider a case involving one who was ritually pure when he entered the Temple but who became impure while in the Temple courtyard, and afterward, his impurity was hidden from him but he remembered that he was standing in the Temple, or the fact that he was standing in the Temple was hidden from him but he remembered his impurity, or both this fact and that fact were hidden from him. In all these cases, if he bowed down, or he tarried in the Temple courtyard long enough to bow down even though he did not actually bow, or he went out by way of a longer route when he could have taken a shorter route, he is liable to bring a sliding-scale offering. But if he left the Temple via the shortest way, he is exempt. This mitzva that the ritually impure must be sent out of the Temple is the positive mitzva concerning the Temple for which, as is taught elsewhere in the Mishna (Horayot 8b), the Sanhedrin is not liable to bring an offering for an erroneous ruling. A communal bull sin-offering is brought because of the unwitting transgression of a prohibition involving an action by the Jewish people resulting from an erroneous halakhic decision handed down by the Sanhedrin. But if the Sanhedrin mistakenly ruled that one who became impure while in the Temple may leave by way of a longer route, they do not bring this offering, as it is brought only for an erroneous ruling on a matter that requires the bringing of a fixed sin-offering, and not a sliding-scale offering, for its unwitting violation.

נִטְמָא בָעֲזָרָה וְנֶעֶלְמָה מִמֶּנּוּ טֻמְאָה וְזָכוּר אֶת הַמִּקְדָּשׁ, נֶעְלַם מִמֶּנּוּ מִקְדָּשׁ וְזָכוּר לַטֻּמְאָה, נֶעְלַם מִמֶּנּוּ זֶה וָזֶה, וְהִשְׁתַּחֲוָה אוֹ שֶׁשָּׁהָה בִכְדֵי הִשְׁתַּחֲוָאָה, בָּא לוֹ בָאֲרֻכָּה, חַיָּב. בַּקְּצָרָה, פָּטוּר. זוֹ הִיא מִצְוַת עֲשֵׂה שֶׁבַּמִּקְדָּשׁ, שֶׁאֵין חַיָּבִין עָלֶיהָ:

And which is the positive mitzva with regard to a menstruating woman for which, as is taught in Horayot there, the Sanhedrin is liable to bring a bull offering for an erroneous ruling? If a man was engaging in intercourse with a ritually pure woman, and during the course of their act of intercourse she experienced menstrual bleeding and said to him: I have become impure, and unwittingly he immediately withdrew from her and did not wait until his penis became flaccid, he is liable to bring a sin-offering for engaging in intercourse with a menstruating woman, because his withdrawal from her is as pleasant to him as his entry. If the Sanhedrin mistakenly ruled that one may withdraw immediately, they bring a bull offering for their erroneous ruling.

וְאֵיזוֹ הִיא מִצְוַת עֲשֵׂה שֶׁבַּנִּדָּה שֶׁחַיָּבִין עָלֶיהָ, הָיָה מְשַׁמֵּשׁ עִם הַטְּהוֹרָה וְאָמְרָה לוֹ נִטְמֵאתִי, וּפֵרַשׁ מִיָּד, חַיָּב, מִפְּנֵי שֶׁיְּצִיאָתוֹ הֲנָאָה לוֹ כְּבִיאָתוֹ: