On par for a man who has been told he is literally in the last throes of his life (Numbers 31:2), Moses wants to make sure that his house is in order before he leaves Israel for good.
It must’ve come as a shock for him then when Gad and Reuben showed up in his office with a request to settle in the Transjordan area, instead of marching across the Jordan and conquering Canaan with his brothers.
To be fair, the whole thing is a misunderstanding. After Moses’ monologue in Numbers 32, Reuben and Gad state their desire to take Canaan; they simply want the Transjordan for an inheritance. For his part, Moses agrees to that arrangement.
But Moses doesn’t know that yet. His initial rebuke of these two tribes in the meantime is multi-layered. Clearly still struggling with the PTSD of the revolt in Numbers 13-14, where ten spies discouraged the entire nation from their march into Canaan, Moses reacts with anger.
Moreover, he invokes God’s anger. He reminds them how this exact situation resulted in a forty-year punishment for the previous generation. Their refusal to enter Canaan was based on fear. Is it possible Reuben and Gad are guilty of the same thing? In the end, are they just cowards?
To Moses, the entire request is selfish. If Gad and Reuben are allowed to stay on the other side of the Jordan, God will “abandon them in the wilderness,” and every one of the tribes will perish as a result.
And for what? So a couple tribes can have some awesome pasture land? That won’t fly with a man who has led so selflessly the last forty years to get the nation to this very point. He won’t abide two tribes messing it up now.
Even though it’s not expressly stated here, I would imagine Moses also detects a bit of division here, as well. It won’t be until the time of Saul that the nation of Israel really has a unified, national identity, but a request like this could lead to isolationism. Before long, Gad and Reuben may not even claim to be a part of God’s people.
But look at the word that Moses himself uses for the real reason he reacts: discouragement. In his mind, if he allows these two tribes to stay on the other side of the Jordan, it’ll signal to the rest of the nation that they’re going in short-handed.
And, maybe, that the land isn’t worth fighting for anyways. After all, if Reuben and Gad can just claim whatever land they want, why can’t all of them? What’s stopping Asher from trekking north? What if Judah really liked the Wilderness of Sinai that they just spent forty years marching through?
Most likely, you’ve seen this type of discouragement in action. A group is fired up about a project, only to have Sally-Don’t-Care on the sidelines poo-pooing everything. “It won’t work” or “It’s too hard” or “Do we have to do it that way?”
Eventually, that mentality infiltrates everyone else, and then you have a very disillusioned group.
Moses wants to nip that in the bud…now. He won’t stand for it—not with his history with this people. And I don’t blame him one bit.