ARNON (ar'nŏn). The swift “roaring stream” and the valley of the same name that descend to the east side of the Dead Sea a little north of its center. The river begins in the hills of northern Arabia, flows NW a while, and then turns westward to descend precipitously into the Dead Sea, emptying at about the lowest point on the earth’s surface. It is now a “wadi,” implying that it is dry most of the year. It is first mentioned (Num.21.13) as the boundary between the Moabites and the Amorites in the time of Moses; Israel encamped on its north side so as not to invade Moab. In Judg.11.18-Judg.11.26 Jephthah tells the Ammonites how Israel had held the land north of the Arnon for three hundred years previous to this time (c. 1560-1260 b.c.). For all those years, and for a long time after, the Arnon was the southern boundary of the tribe of Reuben. In the days of Jehu (ninth century), Hazael, king of Syria, overpowered Israel east of the Jordan as far as Arnon (2Kgs.10.32-2Kgs.10.33). The Arnon now flows through the kingdom of Jordan.
ARNON är’ nən (אַרְנֹֽון; LXX ̓Αρνών; rushing stream). A river, now dried to a wadi, beginning in the hills of northern Arabia and flowing some twenty m. westward to enter the Dead Sea opposite En-gedi. A network of tributaries referred to as the “valleys of the Arnon” in the Biblical narrative (Num 21:14) add to the flow. For most of its journey, the river now courses through a deep gorge some two m. wide at the top and only some 100 ft. wide at the bottom. The steep banks, rising in places to 1700 ft., are limestone capped with basalt.
The Arnon is first mentioned in the Biblical record as forming the boundary between Moab and the Amorites (Num 21:13). It also formed the southern boundary of the territory assigned to Reuben (Deut 3:12). Israel was commanded to cross the Arnon from S to N and take its first territorial possessions there (Deut 2:24). The Moabite Stone (q.v.) (line 10) indicates, however, that Moabites lived N of the wadi by the time of Omri, thereby implying either incomplete or impermanent settlement by Israel. The river was evidently forded in many places and there are still traces of an old Rom. road and bridge to be seen.
International Standard Bible Encyclopedia (1915)
The modern name of Arnon is Wady el-Mojib, which enters the Dead Sea from the East about 11 miles North of el- Lisan. Some 13 miles East of the Dead Sea two streams, Seil es-Sa`ideh from the South, and Wady Enkeileh from the East, unite their waters and flow westward in the bottom of an enormous trench. The waters of Wady Welch come in from the Northeast. A wide stretch of country thus drains into the valley by means of a great network of smaller wadies--the "valleys of Arnon." The "fords of the Arnon" (Isa 16:2) were doubtless crossed by Mesha’s highway which he claims to have built in Arnon; and may be marked by the traces of the old Roman road and bridge immediately to the West of where, on the northern edge of the Wady, stands `Ara`ir, the ancient Aroer.