Why did Bil'am refer to Yisrael as "ha'Am ha'Yotzei mi'Mitzrayim", as if they had left Egypt of their own accord?
Even though Bil'am knew about Hashem's relationship with Yisrael, his hatred of Yisrael pushed it into the background and he planned to curse them in spite of it. Consequently even when referring to Yetzi'as Mitzrayim, he spoke as if that relationship did not exist.
Why did Bil'am change from "Arah li!" and from va'Agorshenu min ha'Aretz" (which is what Balak asked from him) to "Kabah li" and to "ve'Gerashtiv"?
Rashi: Because "Kabah" is a stronger expression of curse that "Arah", and ve'Gerashtiv!" which means 'I will destroy them from the world', is a stronger expression than "va'Agorshenu min ha'Aretz", which means that he will merely drive them out of the land 1 and he hated Yisrael more than Balak did.
Refer also to Bamidbar 31:2:2:1.
