Or HaChaim on Numbers 22:34/אור החיים על במדבר כ״ב:ל״ד

1 ויאמר בלעם…חטאתי, Bileam said…"I have sinned, etc." The word "I have sinned" referred to the angel having hinted that he had sinned by his having set out on the way. Regarding the angel's question of why he had beaten his ass, Bileam said: "I did not know." The word ועתה means that Bileam had now become a penitent. He no longer wanted to curse the Jewish people Concerrning the fact that he had set out on the way, Bileam offered that if this displeased the angel he was willing to turn back. The word לי meant that he now saw that it would be beneficial for him to go back home.