There was no prophet who described Bnei Yisroel's essence better than Bilam, says Rav Wolbe (Shiurei Chumash). The Ramban writes (Bamidbar 22, 20), Hashem specifically desired that a non-Jewish prophet bless Bnei Yisroel. This is an idea that is already mentioned in the Gemara. Chazal tell us (Avodah Zara 3a) that in the future when Hashem will reward Bnei Yisroel, all the nations of the world will protest that Bnei Yisroel are undeserving since they failed to perform the mitzvos of the Torah. Hashem will respond that gentiles themselves will testify to Bnei Yisroel's vigilance in guarding the Torah's precepts. Lavan will testify that as an employee of twenty years Yaakov didn't take a single item that wasn't his. Nevuchadnetzer will testify that Chananya, Misha'el and Azarya refused to prostrate themselves before the idol, and so on and so forth. Here too, Hashem finds it imperative to bring our arch enemies in testimony to our righteousness.
Rav Wolbe explains this phenomenon as follows. Dovid Hamelech said (Tehillim 92, 12), "When those who would harm me rise up against me, my ears listen." Rav Yisroel Slanter says that when an enemy talks we must listen. If our enemy says that we are righteous, we can be certain that we are truly righteous. However, if he has anything negative to say, then we know we still have what to work on, as the pasuk says, "When Hashem favors a man's ways, even his enemies will make peace with him" (Mishlei 16, 7). Therefore, Hashem is interested in the praises sung by our enemies, for there is not truer praise.
How does Bilam describe Bnei Yisroel? "From the tops of rocks I perceive [them] and from hills do I see it, a nation that will dwell in solitude" (Bamidbar 23, 9). Rashi explains, Bilam was saying that he looked into Bnei Yisroel's origins - the patriarchs and matriarchs - and found that their foundation is rock solid. Every action of our forefathers was committed with the direct intent of creating and building a spiritual nation. Bnei Yisroel were spiritually built into "a nation that will dwell in solitude" andthis is their very essence. We are to be so totally removed from the other nations that the Torah even forbids us to praise them or their possessions.
Bilam perceived that the spiritual construction performed by the Avos was all with the intention of building a nation that will dwell in solitude. Even when living among the other nations, we must bear in mind that Bilam's description is our very essence, and it behooves us to live our lives in accordance with this mentality.