A. The Talking Donkey
As Bilam heads to Moab to curse the Jews, his donkey opens its mouth and berates him (Source 1). If G-d doesn’t perform miracles in vain, asks the Rebbe, why did He make the donkey talk? Seeing the angel would have been enough to stop Bilam.
A similarly spectacular miracle occurs in the story of Korach. Moses goes to the tents of Korach, Datan and Aviram and tells them that if he, Moses is making everything up, they will die a natural death, but if he is a true prophet, the earth will swallow them alive. Indeed, the ground opens up and consumes them (Source 2).
With Korach, the Torah found it necessary to justify the miracle, while here, even Rashi doesn’t comment.
The Ralbag attempts to answer that in fact, the talking donkey was merely a dream, but we can deduce from Rashi that it did actually speak.
B. Saving Bilam From Himself
The Rebbe explains that the angel sent to divert Bilam from the road was an angel of mercy. This is also why G-d opened the donkey’s mouth, to impress Bilam and motivate him to repent (Source 4).
The question, however, remains: G-d certainly knew that opening the donkey’s mouth wouldn’t be effective in turning Bilam around, and the angel would ultimately need to reveal itself to him. Why, then, wasn’t the angel revealed immediately, obviating the need for the talking donkey?
In the Torah reading of Behar, Rashi describes the set of heavenly consequences for one who ignores the mitzvah to keep their fields fallow in the seventh year: First, they lose their money, which causes them in turn to sell off their assets, then they lose their land, then their home, and so on (Source 5). In other words, G-d sends a person signs to repent, progressing in severity with each sign. Bilam, too, was the recipient of such signs, intended to steer him away from transgression. First the donkey began to speak, and then the angel revealed itself.
Story: The Unmovable Wagon
C. The Lesson
Although the subject here is the wicked Bilam, G-d still takes action to prevent him from transgressing. We too, must certainly do everything we can in order to help another Jew, even if it requires much time and effort.
Story: Everyone is important (text and video link included).
Another lesson from here is how careful we must be in treating animals well. The first thing the angel says to Bilam is “Why did you hit your donkey?”
Story: The calf and the mice (text included).