וַיִּפְתַּ֥ח יְהוָ֖ה אֶת־פִּ֣י הָאָת֑וֹן וַתֹּ֤אמֶר לְבִלְעָם֙ מֶה־עָשִׂ֣יתִֽי לְךָ֔ כִּ֣י הִכִּיתַ֔נִי זֶ֖ה שָׁלֹ֥שׁ רְגָלִֽים׃
Da öffnete der Herr den Mund der Eselin, und sie sprach zu Bileam: Was habe ich dir getan, dass du mich nun drei mal geschlagen?
Rashi on Numbers
זה שלש רגלים THESE THREE TIMES — By these words he suggested to him: You seek to root out a nation that celebrates three festivals (שלש רגלים) annually?! (Midrash Tanchuma, Balak 9).
Sforno on Numbers
ויפתח ה' את פי האתון, He provided her with the ability to speak; we are familiar with the verse in Psalms 51,17 which we recite daily before our prayers, asking G’d ה' שפתי תפתח, O Lord please open my lips.” G’d went to all these lengths in order to provide Bileam with yet another incentive to become a penitent. Solomon in Proverbs 16,1 points out מה' מענה לשון, “the answer of the tongue comes from G’d.” Even when man is not prepared to change his way for the better, G’d, on occasion, initiates a step in this direction; how much more so will He extend a helping hand to sinners who seek to mend their ways! All of this in order to save the sinner from perdition.