Mishnah Machshirin 3:6: [If] one's olives were placed on the roof and rain fell upon them, if he is happy [with that] it achieves BeKhi Yutan. Rabbi Yehudah says: It is impossible not to be happy, but if he plugged the gutter or turned them [the olives, it achieves BeKhi Yutan].

הָיוּ זֵיתָיו נְתוּנִים בַּגַּג וְיָרְדוּ עֲלֵיהֶן גְּשָׁמִים, אִם שָׂמַח, בְּכִי יֻתַּן. רַבִּי יְהוּדָה אוֹמֵר, אִי אֶפְשָׁר שֶׁלֹּא לִשְׂמֹחַ, אֶלָּא, אִם פָּקַק אֶת הַצִּנּוֹר אוֹ אִם חִלְחֵל לְתוֹכָן:

Mishnah Machshirin 3:7: [If] donkey drivers were crossing a river and their sacks fell into the water, if they were happy [with that] it achieves BeKhi Yutan. Rabbi Yehudah says: It is impossible not to be happy, but if they turned [the sacks, it achieves BeKhi Yutan]. [If] one's legs were covered in mud as were the legs of his animal [and] he crossed the river, if he is happy [with being cleansed] it achieves BeKhi Yutan [if the water subsequently falls from him onto fruit]. Rabbi Yehudah says: It is impossible not to be happy, but if he stood [in the river] and washed [the water can later achieve BeKhi Yutan]. With a person and a non-kosher animal it is always impure [the water makes food susceptible to impurity].

הַחַמָּרִין שֶׁהָיוּ עוֹבְרִים בַּנָּהָר וְנָפְלוּ שַׂקֵּיהֶם לַמַּיִם, אִם שָׂמְחוּ, בְּכִי יֻתַּן. רַבִּי יְהוּדָה אוֹמֵר, אִי אֶפְשָׁר שֶׁלֹּא לִשְׂמֹחַ, אֶלָּא, אִם הָפְכוּ. הָיוּ רַגְלָיו מְלֵאוֹת טִיט, וְכֵן רַגְלֵי בְהֶמְתּוֹ, עָבַר בַּנָּהָר, אִם שָׂמַח, בְּכִי יֻתַּן. רַבִּי יְהוּדָה אוֹמֵר, אִי אֶפְשָׁר שֶׁלֹּא לִשְׂמֹחַ, אֶלָּא, אִם עָמַד וְהֵדִיחַ. בְּאָדָם וּבִבְהֵמָה טְמֵאָה, לְעוֹלָם טָמֵא: