Mishnah Parah 7:9: One whose waters were on his shoulders and he taught a halachic teaching, showed others the path, killed a snake or a scorpion, or took foods to hide them, it [the water] is invalid. If [he took] food to eat, it is valid; or [killed] a snake or scorpion that were impeding him, it is valid. Rabbi Yehuda says: This is the rule: Anything which is a kind of work, whether or not he stopped [and delayed his way], it is invalid. Anything which is not a kind of work, if he stopped [and delayed his way], it is invalid, and if he did not stop, it is valid.

מִי שֶׁהָיוּ מֵימָיו עַל כְּתֵפוֹ וְהוֹרָה הוֹרָאָה, וְהֶרְאָה לַאֲחֵרִים אֶת הַדֶּרֶךְ, וְהָרַג נָחָשׁ וְעַקְרָב, וְנָטַל אֳכָלִים לְהַצְנִיעָם, פָּסוּל. אֳכָלִין לְאָכְלָן, כָּשֵׁר. הַנָּחָשׁ וְהָעַקְרָב שֶׁהָיוּ מְעַכְּבִים אוֹתוֹ, כָּשֵׁר. אָמַר רַבִּי יְהוּדָה, זֶה הַכְּלָל, כָּל דָּבָר שֶׁהוּא מִשּׁוּם מְלָאכָה, בֵּין עָמַד בֵּין לֹא עָמַד, פָּסוּל. דָּבָר שֶׁאֵינוֹ מִשּׁוּם מְלָאכָה, עָמַד, פָּסוּל. וְאִם לֹא עָמַד, כָּשֵׁר:

Mishnah Parah 7:10: One who leaves his water with a ritually impure individual, it is invalid; and with a ritually pure person, it is valid. Rabbi Eliezer says: even with an impure individual, it is valid if the owner did not do work.

הַמּוֹסֵר מֵימָיו לְטָמֵא, פְּסוּלִין. וּלְטָהוֹר, כְּשֵׁרִין. רַבִּי אֱלִיעֶזֶר אוֹמֵר, אַף לְטָמֵא כְּשֵׁרִין, אִם לֹא עָשׂוּ הַבְּעָלִים מְלָאכָה: