The tribe of Reuben is mentioned first in the lists given in Exodus 1:1-4; Numbers 1:5, 20, 21, but in the later lists it follows others (Num 2:10); the leadership belonged to Judah (2:3). In the line of march through the wilderness Reuben led the second division that followed the Levites, who transported the Tabernacle (Num 10:17, 18).

At the time of the Conquest the tribe of Reuben along with the tribe of Gad and the half-tribe of Manasseh petitioned for the right to remain on the high plateau E of the Jordan where there was ample room for grazing cattle. The permission was granted on condition that they would give military support to the tribes on the W bank of the river until the latter had completed the subjugation of the land (Num 32:1-32; Josh 4:12, 13). In Moses’ final partition of the land this agreement was confirmed, and the E bank of the Jordan became the heritage of the tribes of Reuben, Gad, and Manasseh (Josh 13:8-23; 18:7).

Severed from the other tribes by the valley of the Jordan, the tribes of Reuben, Gad, and the half-tribe of Manasseh felt alienated from the others, and wanted to have a center of worship for themselves. They established an altar of their own, which the western tribes interpreted as a move toward religious secession. The latter threatened war, but the eastern tribes disavowed any desire to desert the worship of Yahweh. On the contrary, they did not wish to be excluded from the united worship of the nation. A war was averted, and the issue was closed (Josh 22:10-34).

The name of Reuben occurs only once in the NT in the enumeration of the tribes comprised in the sealing of the 144,000 (Rev 7:5).

International Standard Bible Encyclopedia (1915)

roo’-ben, ru’-ben (re’ubhen; Rhouben): The eldest son of Jacob, born to him by Leah in Paddan-aram (Ge 29:32).

1. Jacob’s Oldest Son:

The incidents recorded are regarded by a certain school of Old Testament scholars as the vague and fragmentary traditions of the tribe, wrought into the form of a biography of the supposed ancestor of the tribe. This interpretation raises more difficulties than it solves, and depends for coherence upon too many assumptions and conjectures. The narrative as it stands is quite intelligible and self-consistent. There is no good reason to doubt that, as far as it goes, it is an authentic record of the life of Jacob’s son.

2. Tribal History:

At the first census in the wilderness Reuben numbered 46,500 men of war (Nu 1:21); at the second they had fallen to 43,730; see Numbers. The standard of the camp of Reuben was on the south side of the tabernacle; and with him were Simeon and Gad; the total number of fighting men in this division being 151,450. Targum Pseudo-Jonathan says that the standard was a deer, with the legend "Hear O Israel, the Lord thy God is one Lord." On the march this division took the second place (Nu 2:10 ). The prince of the tribe was Elizur ben Shedeur, whose oblation is described in Nu 7:30 ff. The Reubenite among the spies was Shammua ben Zaccur (13:4). It is possible that the conspiracy against Moses, organized by the Reubenites Dathan and Abiram, with the assistance of Korah the Levite (Nu 16), was an attempt on the part of the tribe to assert its rights as representing the firstborn. It is significant that the children of Korah did not perish (26:11). May not the influence of this incident on Moses’ mind be traced in his "blessing," wishing for the continuance of the tribe, indeed, but not in great strength (De 33:6)? This was a true forecast of the tribal history.

When the high plateau East of the Dead Sea and the Jordan fell into the hands of the Israelite invaders, these spacious pastoral uplands irresistibly attracted the great flock-masters of Reuben and Gad, two tribes destined to be neighbors during succeeding centuries. At their earnest request Moses allowed them their tribal possessions here subject to one condition, which they loyally accepted. They should not "sit here," and so discourage their brethren who went to war beyond the Jordan. They should provide for the security of their cattle, fortify cities to protect their little ones and their wives from the inhabitants of the land, and their men of war should go before the host in the campaign of conquest until the children of Israel should have inherited every man his inheritance (Nu 32:1-27). Of the actual part they took in that warfare there is no record, but perhaps "the stone of Bohan the son of Reuben" (Jos 15:6; 18:17) marked some memorable deed of valor by a member of the tribe. At the end of the campaign the men of Reuben, having earned the gratitude of the western tribes, enriched by their share of the spoils of the enemy, returned with honor to their new home. Along with their brethren of Gad they felt the dangers attaching to their position of isolation, cut off from the rest of their people by the great cleft of the Jordan valley. They reared therefore the massive altar of Ed in the valley, so that in the very throat of that instrument of severance there might be a perpetual witness to themselves and to their children of the essential unity of Israel. The western tribes misunderstood the action and, dreading religious schism, gathered in force to stamp it out. Explanations followed which were entirely satisfactory, and a threatening danger was averted (Jos 22). But the instincts of the eastern tribes were right, as subsequent history was to prove. The Jordan valley was but one of many causes of sundering. The whole circumstances and conditions of life on the East differed widely from those on the West of the river, pastoral pursuits and life in the open being contrasted with agricultural and city life.

The land given by Moses to the tribe of Reuben reached from the Arnon, Wady el-Mojib, in the South, to the border of Gad in the North. In Nu 32:34 cities of Gad are named which lay far South, Aroer being on the very lip of the Arnon; but these are probably to be taken as an enclave in the territory of Reuben. From Jos 13:15 ff it is clear that the northern border ran from some point North of the Dead Sea in a direction East-Northeast, passing to the North of Heshbon. The Dead Sea formed the western boundary, and it marched with the desert on the East. No doubt many districts changed hands in the course of the history. At the invasion of Tiglath-pileser, e.g., we read that Aroer was in the hands of the Reubenites, "and eastward .... even unto the entrance of the wilderness from the river Euphrates" (1Ch 5:8 f). Bezer the city of refuge lay in Reuben’s territory (Jos 20:8, etc.). A general description of the country will be found under MOAB; while the cities of Reuben are dealt with in separate articles.

The subsequent history of the tribe is left in much obscurity. Exposed as they were to hostile influences of Moab and the East, and cut off from fellowship with their brethren in worship, in their isolation they probably found the descent into idolatry all too easy, and the once powerful tribe sank into comparative insignificance. Of the immediate causes of this decline we have no knowledge. Moab established its authority over the land that had belonged to Reuben; and Mesha, in his inscription (M S), while he speaks of Gad, does not think Reuben worthy of mention. They had probably become largely absorbed in the northern tribe. They are named as suffering in the invasion of Hazael during the reign of Jehu (2Ki 10:32 f). That "they trespassed against the God of their fathers, and played the harlot after the gods of the peoples of the land" is given as the reason for the fate that befell them at the hands of Pul, king of Assyria, who carried them away, "and brought them unto Halah, and Habor, and Hara, and to the river of Gozan" (1Ch 5:25 f).

The resemblance of Reuben’s case to that of Simeon is striking, for Simeon also appears to have been practically absorbed in the tribe of Judah. The prestige that should have been Reuben’s in virtue of his birthright is said to have passed to Joseph (1Ch 5:1). And the place of Reuben and Simeon in Israel is taken by the sons of Joseph, a fact referred to in the blessing of Jacob (Ge 48:5).

Ezekiel finds a place for Reuben in his picture of restored Israel (48:6). He appears also--in this case preceded by Judah only--in Re 7:5.