סוטה ו׳Sotah 6

Mishnah 3ג׳

שֶׁהָיָה בְדִין, וּמָה אִם עֵדוּת רִאשׁוֹנָה שֶׁאֵין אוֹסַרְתָּהּ אִסּוּר עוֹלָם, אֵינָהּ מִתְקַיֶּמֶת בְּפָחוֹת מִשְּׁנַיִם, עֵדוּת אַחֲרוֹנָה שֶׁאוֹסַרְתָּהּ אִסּוּר עוֹלָם, אֵינוֹ דִין שֶׁלֹּא תִתְקַיֵּם בְּפָחוֹת מִשְּׁנָיִם, תַּלְמוּד לוֹמַר וְעֵד אֵין בָּהּ, כָּל עֵדוּת שֶׁיֵּשׁ בָּהּ. קַל וָחֹמֶר לָעֵדוּת הָרִאשׁוֹנָה מֵעַתָּה, וּמָה אִם עֵדוּת אַחֲרוֹנָה שֶׁאוֹסַרְתָּהּ אִסּוּר עוֹלָם, הֲרֵי הִיא מִתְקַיֶּמֶת בְּעֵד אֶחָד, עֵדוּת הָרִאשׁוֹנָה שֶׁאֵין אוֹסַרְתָּהּ אִסּוּר עוֹלָם, אֵינוֹ דִין שֶׁתִּתְקַיֵּם בְּעֵד אֶחָד, תַּלְמוּד לוֹמַר (דברים כד) כִּי מָצָא בָהּ עֶרְוַת דָּבָר, וּלְהַלָּן הוּא אוֹמֵר (שם יט), עַל פִּי שְׁנֵי עֵדִים יָקוּם דָּבָר, מַה לְּהַלָּן עַל פִּי שְׁנַיִם עֵדִים, אַף כָּאן עַל פִּי שְׁנַיִם עֵדִים:

This is how it would be according to logic: Just like the first testimony [of warning], that doesn't make her prohibited forever [from being married to him], is only valid through two [witnesses], so too the last testimony [of seclusion], that does forbid her forever -- is it not logical that it should only be valid with two [witnesses]? So the verse comes to teach:"and there was no witness against her" (Numbers 5:13) -- any testimony that there is against her. There is a kal vachomer [logical induction from minor to major] from this! Just like the last testimony prohibits her [from her husband] forever and is valid through one witness, the first testimony that doesn't prohibit her forever -- is it not logical that it should be valid with one witness? So the verse comes to teach: (Deuteronomy 24:1) "When he finds in her an unseemly thing," (Deuteronomy 24:1) and earlier it says: "through two witnesses the thing will be upheld" (Deuteronomy 19:15) . Just like earlier it [the testimony] is through two witnesses, so too here it is through two witnesses.

Mishnah 4ד׳

עֵד אוֹמֵר נִטְמֵאת וְעֵד אוֹמֵר לֹא נִטְמֵאת, אִשָּׁה אוֹמֶרֶת נִטְמֵאת וְאִשָּׁה אוֹמֶרֶת לֹא נִטְמֵאת, הָיְתָה שׁוֹתָה. אֶחָד אוֹמֵר נִטְמֵאת וּשְׁנַיִם אוֹמְרִים לֹא נִטְמֵאת, הָיְתָה שׁוֹתָה. שְׁנַיִם אוֹמְרִים נִטְמֵאת וְאֶחָד אוֹמֵר לֹא נִטְמֵאת, לֹא הָיְתָה שׁוֹתָה:

[If] one witness says "she became impure" and [another] witness says "she did not become impure;" or a woman says "she became impure" and [another] woman says "she did not become impure," she would drink [the bitter waters]. [If] one [witness] says "she became impure" and two [witnesses] say "she did not become impure," she would drink [the bitter waters]. [If] two [witnesses] say "she became impure" and one [witness] says "she did not become impure," she would not drink [the bitter waters].