In parsha Matos, the Torah tells us that prior to entering Canaan, the tribes of Gad and Reuvein came to Moshe with a request to give them their
share of the land east of the Jordan River in the lands Bnai Yisroel had conquered, and that they were willing to forego their portion in Canaan. Moshe became furious with them, citing the refusal of the earlier generation to conquer Canaan, which resulted in their wandering in the desert for forty years.
Moshe became furious with them. "Ha'acheichem yavo'uh lamilchama v'atem teishvu poh - Your brethren will go to war and you will stay here?" (Bamidbar 32:6.) Your fathers reject the land Hashem promised us, and, "V'hinei kamtem tachas avoseichem tarbus anashim chatoim lispos od al charon af Hashem el Yisroel - Now you have arisen in the place of your fathers, a society of sinful people, to add more to the burning wrath of Hashem against Israel" (Bamidbar 32:14.)
The tribes of Gad and Reuvein explained that they would never think of shirking their responsibility in the conquest of Canaan. To the contrary, they were willing to go head as a vanguard, and after Canaan was successfully conquered, they would then return to settle in Eiver haYarden. Moshe agreed to this.
But why was Moshe so quick in condemning them, telling them that they are as bad as their fathers? Why didn't he give them a chance to explain themselves?
When Moshe related the incident of the spies that had occurred forty years earlier, he expressed his guilt in the episode, saying that when they requested scouting the land, "The idea was good in my eyes." But why should he have felt guilty? The answer is in Rashi's comment on Moshe's statement, "All of you approached me," to which Moshe said, "You came as an undisciplined mob, the young pushing aside the old, and elders pushing aside the leaders." Moshe's confession of guilt was, "I should have known that with the gross disrespect you exhibited, the venture you suggested would not come to any good result."
During the forty years in the desert, Moshe taught Bnai Yisroel Torah, teaching them proper middos, and he had hoped that they had refined their character traits. But look carefully at the words in the Torah, "Vayavo'uh bnai Gad u'bnai Reuvein - The tribe of Gad and the tribe of Reuvein came to Moshe" (Bamidbar 32:2.) Reuvein was the oldest of Yaakov's sons, and Gad was much younger. When they came to Moshe, the tribe of Gad had pushed the tribe of Reuvein aside! Moshe was horrified by this. "After forty years of my teaching you middos, you obviously have learned nothing! The younger are still pushing themselves ahead of the older. You haven't changed a bit! You are following in the chutzpadik footsteps of your fathers!" No wonder that Moshe was enraged. Because they manifested such poor middos, Moshe assumed that they would shirk their responsibility to the nation.
Proper middos are the foundation of Torah. Rebbe Chiam Vital, the prime disciple of the Ari z"l said that a person must be even more cautious and stringent in practicing fine middos than in the observance of both the positive and restrictive mitzvos (Shaar Hakedushah 2:2).
The mussar teachers bewailed the behavior of students who pushed aside others in order to sit next to the speaker. It is hypocritical and a violation of mussar to be inconsiderate of others in the effort to hear a lecture on mussar!
The episode of the tribes of Gad and Reuvein is an important lesson in derech eretz.