Mishnah Parah 8:11: Achav's well and the cave of Pamyas are valid. Waters which were changed [in appearance] and the change occurred by itself are valid. A channel of water which came from afar is valid, so long as it was guarded such that [it is known] that a person did not stop it [in its flow from the spring]. Rabbi Yehuda says: Behold, it is presumed to be permitted [i.e. even without guarding it is presumed that no one stopped its flow]. A well into which fell earthenware shards or earth, one should wait [before using the water] until it becomes clear, according to Rabbi Yishmael; Rabbi Akiva says: There is no need to wait.

בְּאֵר אַחְאָב וּמְעָרַת פַּמְיָס, כְּשֵׁרָה. הַמַּיִם שֶׁנִּשְׁתַּנּוּ וְשִׁנּוּיָן מֵחֲמַת עַצְמָן, כְּשֵׁרִין. אַמַּת הַמַּיִם הַבָּאָה מֵרָחוֹק, כְּשֵׁרָה, וּבִלְבַד שֶׁיִּשְׁמְרֶנָּה שֶׁלֹּא יַפְסִיקֶנָּה אָדָם. רַבִּי יְהוּדָה אוֹמֵר, הֲרֵי הִיא בְחֶזְקַת מֻתֶּרֶת. בְּאֵר שֶׁנָּפַל לְתוֹכָהּ חַרְסִית אוֹ אֲדָמָה, יַמְתִּין לָהּ עַד שֶׁתִּצַּל, דִּבְרֵי רַבִּי יִשְׁמָעֵאל. רַבִּי עֲקִיבָא אוֹמֵר, אֵינוֹ צָרִיךְ לְהַמְתִּין:

Mishnah Parah 9:1: A flask [of water which has already been mixed with ashes and sanctified] into which an[y] amount of water fell, Rabbi Eliezer says: One should sprinkle two sprinklings [instead of one, on a ritually impure individual in order to purify him]; and the Sages invalidate [the waters]. If dew fell into it, Rabbi Eliezer says: One should leave it in the sun and the dew will rise [i.e. evaporate]; and the Sages invalidate [the water]. If liquids or fruit juices fell into it, one should pour it out [because it has been invalidated], and drying [of the vessel before reuse] is required. If ink, or coloured charcoal, or coloured water, or anything which leaves a mark [fell into the water], one should pour it out [because it has been invalidated] and drying [the vessel before reuse] is not required.

צְלוֹחִית שֶׁנָּפַל לְתוֹכָהּ מַיִם כָּל שֶׁהֵן, רַבִּי אֱלִיעֶזֶר אוֹמֵר, יַזֶּה שְׁתֵּי הַזָּיוֹת. וַחֲכָמִים פּוֹסְלִין. יָרַד לְתוֹכָהּ טַל, רַבִּי אֱלִיעֶזֶר אוֹמֵר, יַנִּיחֶנָּה בַחַמָּה וְהַטַּל עוֹלֶה. וַחֲכָמִים פּוֹסְלִין. נָפַל לְתוֹכָהּ מַשְׁקִין וּמֵי פֵרוֹת, יְעָרֶה וְצָרִיךְ לְנַגֵּב. דְּיוֹ, קוֹמוֹס, וְקַנְקַנְתּוֹם, וְכָל דָּבָר שֶׁהוּא רוֹשֵׁם, יְעָרֶה וְאֵינוֹ צָרִיךְ לְנַגֵּב: