It’s been awhile, so let me give you a quick recap. God told Moses to genocide the Midianites, and they murdered them all except for the virgin girls who they kept as sex slaves. They also kept all the livestock and treasure and divided it up in a most unfair manner. And magically, during the entire war, not a single Israelite was killed. And now we start Numbers 32, which I’m sure will be just as believable!
The the ancestors of Reuben and Gad have noticed something rather interesting. Since God has led them on a bloody rampage all throughout the land, there is nobody left alive to defend it. The lands of Jazer, Ataroth, Dibon, Nimrah, Heshbon, Elealeh, Sebam, Nebo and Beon could easily be settled upon as they are good for raising livestock (as good as a rocky desert terrain can get, anyway).
Now, even though the Israelites are pitiless killing machines, they are making a pretty good point here. Why bother going to war with several more cultures in the Promised Land when they’ve already murdered everyone here? Plus, all that blood will really enrich the soil! What would make this an even better—and less-selfish—idea, is if the Reubenites and the Gadites wanted all the Israelites to live here in harmony rather than just themselves, but at least they’ve grown tired of all the murdering.
But Moses isn’t having any of that! He chastises them for wanting to live out a peaceful existence here while the rest of the Israelites fulfill God’s command to murder several more entire societies. Then, he compares the Reubenites and Gadites to their fathers who were also too afraid to invade an obviously superior, and might I add innocent, enemy.
If Moses is mocking them for their fathers, then quite a bit of time must have taken place since the spies gave their report on the military capabilities of Canaan. It would have been nice if the authors mentioned that, but by now we should be used to incoherent time lines. Of course, if you remember, in God’s perfect fairness, he has been, and will continue to punish the spies’ children for four generations, so can you really blame them for wanting out of this mess?