Numbers 32 tests whether the new generation has learned from the old. The children of Reuben and Gad had a very great multitude of livestock, and the land of Jazer and Gilead was a place for livestock. They asked, Don't bring us over the Jordan. Moses heard echoes of Kadesh: Shall your brothers go to war while you sit here? Why do you discourage the heart of the children of Israel from going over into the land which Yahweh has given them? Your fathers did so. If they turned away, God would again leave Israel in the wilderness.
The tribes came near with a careful proposal. We will build sheepfolds here for our livestock, and cities for our little ones; but we ourselves will be ready armed to go before the children of Israel. We will not return to our houses until the children of Israel have all received their inheritance. Moses accepted, provided they kept their word before Yahweh.
Then came the famous warning: But if you will not do so, behold, you have sinned against Yahweh; and be sure your sin will find you out. In context, the sin would be failing to keep their promise and leaving their brothers to fight alone. Moses commanded Eleazar and Joshua to hold them to it, and gave the kingdoms of Sihon and Og to Gad, Reuben, and the half-tribe of Manasseh. Joshua 22:1-4 later praises them for not leaving their brothers. Paul urges believers to bear one another's burdens (Galatians 6:2).