Midrasch zu Bamidbar 22:30
וַתֹּ֨אמֶר הָאָת֜וֹן אֶל־בִּלְעָ֗ם הֲלוֹא֩ אָנֹכִ֨י אֲתֹֽנְךָ֜ אֲשֶׁר־רָכַ֣בְתָּ עָלַ֗י מֵעֽוֹדְךָ֙ עַד־הַיּ֣וֹם הַזֶּ֔ה הַֽהַסְכֵּ֣ן הִסְכַּ֔נְתִּי לַעֲשׂ֥וֹת לְךָ֖ כֹּ֑ה וַיֹּ֖אמֶר לֹֽא׃
Die Eselin sprach zu Bileam: Bin ich doch deine Eselin, auf der du geritten von jeher bis auf den heutigen Tag; bin ichs gewohnt, dir also zu tun? Und er sprach: Nein!
Bamidbar Rabbah
... [T]he Holy One has pity on the honor of the creatures/b’riyot (here meaning “people”) and knows their needs. And He shut the mouth of the beast/b’heimah, for if she would speak, they could not make her serve or stand up to her /bah, for [there was] this silent one from the animals (the ass) and this wise one from the sages (Bil`am) – [and] when she spoke he could not stand up to her.
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