מקואות ב׳Mikvaot 2

Mishnah 1א׳

הַטָּמֵא שֶׁיָּרַד לִטְבֹּל, סָפֵק טָבַל סָפֵק לֹא טָבַל, אֲפִלּוּ טָבַל, סָפֵק יֶשׁ בּוֹ אַרְבָּעִים סְאָה סָפֵק אֵין בּוֹ. שְׁנֵי מִקְוָאוֹת, אֶחָד יֶשׁ בּוֹ אַרְבָּעִים סְאָה וְאֶחָד שֶׁאֵין בּוֹ, טָבַל בְּאַחַד מֵהֶם וְאֵינוֹ יוֹדֵעַ בְּאֵיזֶה מֵהֶן טָבַל, סְפֵקוֹ טָמֵא:

Someone who went down to immerse [in a mikveh], and there is an uncertainty as to whether he immersed or not, or an uncertainty as to whether it contained forty se'ah [a specific unit of volume] in it or it did not; or if there were two mikva'ot [gatherings of water collected by natural means and immersed in for purification], one with forty se'ah in it, and one without, and someone immersed in one of them but he does not know in which one he immersed, its uncertainty is impure [i.e. the case is uncertain and resolved as impure].

Mishnah 2ב׳

מִקְוֶה שֶׁנִּמְדַּד וְנִמְצָא חָסֵר, כָּל טָהֳרוֹת שֶׁנַּעֲשׂוּ עַל גַּבָּיו לְמַפְרֵעַ, בֵּין בִּרְשׁוּת הַיָּחִיד בֵּין בִּרְשׁוּת הָרַבִּים, טְמֵאוֹת. בַּמֶּה דְבָרִים אֲמוּרִים, בְּטֻמְאָה חֲמוּרָה. אֲבָל בְּטֻמְאָה קַלָּה, כְּגוֹן אָכַל אֳכָלִים טְמֵאִים, וְשָׁתָה מַשְׁקִין טְמֵאִים, בָּא רֹאשׁוֹ וְרֻבּוֹ בְּמַיִם שְׁאוּבִים, אוֹ שֶׁנָּפְלוּ עַל רֹאשׁוֹ וְעַל רֻבּוֹ שְׁלשָׁה לֻגִּין מַיִם שְׁאוּבִין, וְיָרַד לִטְבֹּל, סָפֵק טָבַל סָפֵק לֹא טָבַל, אֲפִלּוּ טָבַל, סָפֵק יֶשׁ בּוֹ אַרְבָּעִים סְאָה סָפֵק אֵין בּוֹ. שְׁנֵי מִקְוָאוֹת, אֶחָד יֶשׁ בּוֹ אַרְבָּעִים סְאָה, וְאֶחָד שֶׁאֵין בּוֹ, טָבַל בְּאַחַד מֵהֶן וְאֵינוֹ יוֹדֵעַ בְּאֵיזֶה מֵהֶן טָבַל, סְפֵקוֹ טָהוֹר. רַבִּי יוֹסֵי מְטַמֵּא, שֶׁרַבִּי יוֹסֵי אוֹמֵר, כָּל דָּבָר שֶׁהוּא בְחֶזְקַת טֻמְאָה, לְעוֹלָם הוּא בִפְסוּלוֹ, עַד שֶׁיִּוָּדַע שֶׁטָּהַר. אֲבָל סְפֵקוֹ לִטָּמֵא וּלְטַמֵּא, טָהוֹר:

A mikveh which was measured and found to be lacking [the required forty se'ah of water], all purifications which were made upon it, whether in a private domain or in a public domain, are retroactively impure. To what [cases] does this apply? To a severe impurity [i.e something that was rendered impure by an Origin of impurity]. But with a light impurity, such as one who ate impure foods, or drank impure drinks, or one whose head and the majority of his body entered into drawn waters, or if three log [a specific measure of volume] of drawn water fell on one's head and the majority of one's body and one then went down to immerse; [in such a cases,] if there is an uncertainty as to whether he immersed or not, or even if he immersed, if there is an uncertainty as to whether it contained forty se'ah in it or it did not, or if there were two mikva'ot, one with forty se'ah in it and one without, and he immersed in one of them but does not know in which one he immersed, [in such cases,] its uncertainty is pure [i.e. the cases are uncertain and resolved as pure]. Rabbi Yose considers it impure, as Rabbi Yose says: Everything which has a presumption of impurity remains forever in its invalid state, until it becomes known that it was purified. But its uncertainty [regarding its ability] to become impure or to render [something else] impure, is pure [i.e. such cases are uncertain and resolved as pure].