The plunder from the conquest of Midian was to be divided between the army that fought and the rest of the congregation. They were to levy a tribute for the Lord on the men of war. The tribute from the men of war was to be 1 of every 100 people, animals, , etc. From the congregation, the tribute would be 1 of every 50 people and animals. The tribute would be given to the priest, Eleazar, and the Levites. The leaders of the army and the congregation also gave offerings of the gold and jewelry collected.
The tribes of Reuben and Gad had great livestock and found the land of Jazer and Gilead good for livestock. They asked if they could settle on the Eastern side of Jordan, rather than crossing over with their great flocks. Moses questioned the request, thinking they would not help the other tribes fight to take the land of Canaan. He reminded them of the penalty for disbelief levied upon those who did not believe they could take the promised land about 40 years earlier. However, the tribes of Reuben and Gad responded that they wanted to establish cities for their families and sheepfolds for their flocks. After that, they would then go across the Jordan to help the rest take the land. The agreement was reached and Reuben, Gad, and the half-tribe of Manasseh took the land of the Amorites, and built cities and sheepfolds.
The story of the plunder is a picture of thankfulness and gratitude to God. When they came back from war, they recognized that every blessing is from God, and that He is worthy of praise, but also tribute. This is related to the principle of tithing and giving, and is an act of worship.
The two and 1/2 tribes that stayed on the East Side of Jordan brought back bad memories for Moses, as it smacked of the faithlessness of the Israelites 40 years earlier. Moses made sure that they knew the consequences of faithlessness, and an agreement was made that secured Israel’s conquest of the promise land and provided Reuben, Gad, and Manasseh the land they needed for their flocks.