Numbers 32:14 And, behold, ye are risen up in your fathers’ stead, an increase of sinful men, to augment yet the fierce anger of the LORD toward Israel.
Two and a half tribes do not want to cross over the Jordan into the promised land. They want to stay on the other side, away from what God had promised. Moses gets angry. God had given them land. Why were they coming up with another plan?
He saw this new plan as something similar to what had happened with the ten wicked spies. He didn’t want to see the people decide not to do the Lord’s will. These people will promise to honor God, and everything will end up working out. Moses has spoken rashly and harshly.
At the same time, we should all be ready to stand against half-hearted commitment. People want to go almost to the promise. They decide how much of God’s will they want. That would aggravate Moses as well as it should aggravate us.