Reference for Makhshirin 4:5
עֲרֵבָה שֶׁיָּרַד הַדֶּלֶף לְתוֹכָהּ, הַנִּתָּזִין וְהַצָּפִין אֵינָן בְּכִי יֻתַּן. נְטָלָהּ לְשָׁפְכָהּ, בֵּית שַׁמַּאי אוֹמְרִים, בְּכִי יֻתַּן. בֵּית הִלֵּל אוֹמְרִים, אֵינָן בְּכִי יֻתַּן. הִנִּיחָהּ שֶׁיֵּרֵד הַדֶּלֶף לְתוֹכָהּ, הַנִּתָּזִין וְהַצָּפִין, בֵּית שַׁמַּאי אוֹמְרִים, בְּכִי יֻתַּן. בֵּית הִלֵּל אוֹמְרִים, אֵינָן בְּכִי יֻתַּן. נְטָלָהּ לְשָׁפְכָהּ, אֵלּוּ וָאֵלּוּ מוֹדִים שֶׁהֵן בְּכִי יֻתַּן. הַמַּטְבִּיל אֶת הַכֵּלִים וְהַמְכַבֵּס אֶת כְּסוּתוֹ בִּמְעָרָה, הַמַּיִם הָעוֹלִים בְּיָדָיו, בְּכִי יֻתַּן. בְּרַגְלָיו, אֵינָן בְּכִי יֻתַּן. רַבִּי אֶלְעָזָר אוֹמֵר, אִם אִי אֶפְשָׁר לוֹ שֶׁיֵּרֵד אֶלָּא אִם כֵּן נִטַּנְּפוּ רַגְלָיו, אַף הָעוֹלִין בְּרַגְלָיו בְּכִי יֻתַּן:
[If] rain water dripped into a trough, [water] that splashed [out] or that overflowed does not achieve <i>BeKhi Yutan</i>. [If] he took it [the trough] to pour out [the water] Beit Shammai say: That achieves <i>BeKhi Yutan</i> [if the water subsequently falls onto fruit]; Beit Hillel say: That does not achieve <i>BeKhi Yutan</i>. [If] he [initially] placed the trough so [the water] would drip into it, Beit Shammai say: Its [water] that splashes out or that overflows achieves <i>BeKhi Yutan</i>. Beit Hillel say: That does not achieve <i>BeKhi Yutan</i>. [If] he took it [the trough] to pour out [the water] both [schools] agree that that achieves <i>BeKhi Yutan</i>. [If] one immerses vessels or washes his clothing in a cave, the water that comes up on his hands achieves <i>BeKhi Yutan</i>; [water that comes off] his legs does not achieve <i>BeKhi Yutan</i>. Rabbi Elazar says: If he cannot descend to the cave without his legs getting dirty, even [the water] that comes up on his legs achieves <i>BeKhi Yutan</i>.