וַתֵּ֨רֶא הָאָת֜וֹן אֶת־מַלְאַ֣ךְ יְהוָ֗ה וַתִּלָּחֵץ֙ אֶל־הַקִּ֔יר וַתִּלְחַ֛ץ אֶת־רֶ֥גֶל בִּלְעָ֖ם אֶל־הַקִּ֑יר וַיֹּ֖סֶף לְהַכֹּתָֽהּ׃
And the ass saw the angel of the LORD, and she thrust herself unto the wall, and crushed Balaam’s foot against the wall; and he smote her again.
Read kabbalistic (mystical) interpretation of Numbers 22:25: and classical mystical sources.