At first, Moshe Rabbeinu did not intend to conquer the eastern side of the Jordan River, even though it is part of ‘Eretz Yisrael’, the Land of Israel. His intention was first to settle the land of Canaan located on the western side of the Jordan — it being on a higher level of holiness — and from there to consolidate and expand to all the borders of the land. However, Sichon and Og came- out to wage war against Israel, and Israel defeated them and conquered their land.
When the tribes of Reuben and Gad, who possessed enormous amounts of animals, saw that the land was good for grazing, they approached Moshe requesting that he exempt them from crossing over the Jordan, and instead, give them their inheritance on the eastern side, it being suitable for their herds.
Moshe Rabbeinu’s answer was surprisingly harsh. First, he condemned them, saying – “Why should your brothers go out and fight while you stay here?!” (Bamidbar32:6). Furthermore, he blames them for repeating the sin of the Spies who despised the Land of Israel, persuading the nation not to enter the land and thereby arousing God’s anger, to the point where He decreed that the entire generation would die in the desert. And low and behold – here they are, once again, causing Israel to sin and falter by not entering the land! Perhaps, like the Spies, they too will cause a terrible disaster. Moshe chastised them at length, without asking them if their true intentions were in fact not to participate in Israel’s conquering of the land.
When Moshe Rabbeinu finished rebuking them, the members of the tribes of Reuben and Gad answered, saying that their intention was not to evade the war, but rather they would first build enclosures for their sheep and cities for their children, and afterwards, go out as an advance guard in front of Israel to conquer the land. Only after all the tribes were settled in their respective inheritances would they return to their lands on the eastern side of the Jordan. Seemingly, after all this, Moshe Rabbeinu should have been reconciled, perhaps even apologizing for his suspicion. However, Moshe agrees that if they indeed lead Israel in battle, they would be blameless before God and Israel. Nevertheless, from Moshe’s response, it seems he was concerned that they would not fulfill their words. Therefore, he once again requests they commit themselves explicitly — with a double stipulation — concerning their commitment to partake in the conquering of the land.
Ostensibly, Moshe Rabbeinu’s reaction must be questioned: why didn’t he wait to listen to what the tribes of Reuben and Gad had to say? Why did he start to rebuke them with harsh accusations without first clarifying if they were willing to participate in conquering the land? Why, after they told him that they were ready to participate, did he continue to treat them suspiciously?
The reason is that there was a fundamental problem with their desire to inherit the eastern side of the Jordan. Their order of priorities was faulty. Their motive for desiring to inherit that specific portion of the land wasn’t because they felt a deep connection to it, a place where they could fulfill their unique goal of revealing the name of God in the world. Rather, they simply were concerned about their possessions. Moshe Rabbeinu knew that when the initial reason for settling the land does not stem from the exalted value of fulfilling the covenant with God and revealing the Heavenly Presence in the world, their connection to the land would be flimsy, and God forbid, they would lose the land.
Therefore, even after they promised to be the first to go out to war, Moshe Rabbeinu remained suspicious. Although, after they promised to participate in the conquering of the land they were allowed to inherit the eastern side of the Jordan — it also being part of ‘Eretz Yisrael’– nevertheless, if they did not elevate their motives, with the intention of inheriting the land together with all of Israel in order to reveal the word of G-d in the world, they would not be successful.
As our Sages have said (Bamidbar Rabba 22:7), there are wealthy people who don’t understand that wealth is a gift from Heaven. Instead, their riches control them, to the point where they are removed from the world, along with their wealth. “And thus you find concerning the tribes of Reuben and Gad, who were wealthy and possessed large herds. They cherished their wealth and resided outside of the land of Israel. Therefore, they were exiled first amongst all the tribes, as it is written (Chronicles I, 5:26): “…and he carried them away, namely the Re’uveni, and the Gadi, and the half tribe of Menashe.”
What caused this? It was due to the fact that they separated themselves from their brothers because of their possessions”. (The meaning of the Sage’s statement that the tribes of Reuben and Gad resided ‘outside of the land of Israel’ is that they lived outside of the main holiness of the land).