Numbers 32:1
Now the children of Reuben and the children of Gad had a very great multitude of cattle: and when they saw the land of Jazer, and the land of Gilead, that, behold, the place was a place for cattle; Now the children of Reuben and the children of Gad had a very great multitude of cattle: and when they saw the land of Jazer, and the land of Gilead, that, behold, the place was a place for cattle;
The tribes of Reuben and Gad possessed an exceedingly large stock of livestock, embracing both sheep and cattle. Upon surveying the districts of Jazer and Gilead they judged the country to be well adapted to the raising of such flocks and herds. Their request for permission to settle in that region aroused Moses' fear that they meant to withdraw from the warfare their fellow Israelites would still have to wage in taking possession of Canaan.