As the eldest of Jacob’s twelve sons, Reuben had the right to the blessing of the firstborn (Gen 35:23; 46:8). At times he showed qualities of character and leadership (Gen 37:21-30; 42:22,37), but he lost the firstborn’s rights because of his immorality with one of his father’s concubines. As a result the civil leadership of Israel went to the tribe of Judah, the religious leadership to Levi, and the double portion of the inheritance to Joseph. This meant that Joseph received the right to have two tribes (which were descended from his sons, Ephraim and Manasseh) (Gen 35:22; 49:3-4; 1 Chron 5:1-2).
In the time of Moses, certain Reubenites were jealous that a man from the tribe of Levi (Moses), rather than one from the tribe of Reuben, was overall leader in Israel (Num 16:1-3,12-14). God punished their rebellion in a dramatic judgment (Num 16:25-33). When the Israelites conquered and divided Canaan in the time of Joshua, the tribes of Reuben, Gad and half of Manasseh settled east of the Jordan River in territory taken from the Amorites (Num 21:11-35; Josh 13:8-12). This entire eastern territory was often called Gilead, though strictly speaking Gilead was only one part of it (Judg 10:8; 20:1).
(For map and other details see GILEAD.) Reuben was the most southern of the eastern tribes, occupying land that originally belonged to Moab (that is, before Moab lost it to the Amorites) (Num 21:26; Josh 13:15-23). (For the physical features of the region see MOAB.) The reason the two and a half tribes asked for this area was that it had good pasture lands and they had large flocks and herds (Num 32:1-5,33). But their situation east of Jordan separated them from the other tribes, and at times led to tension and misunderstanding (Josh 22:1-34; Judg. 5:16-17). Further difficulties arose for the eastern tribes because their position left them more open to attack than the western tribes (1 Kings 10:32-33). At the time of Israel’s collapse several hundred years later, the eastern tribes were among the first to be taken into captivity (2 Kings 15:29).