IABOG (Hebrew *Jābhōg*). — An eastern tributary of the Jordan. It is famous in the Bible for the night-long struggle waged on its banks (see PHANUEL) by the patriarch Jacob (see), returning from Mesopotamia, with a mysterious figure (Yahweh or the angel of Yahweh?), who changed his name to “Israel” (Gen 32:23–30; 33:17–20). It was near Mahanaim (see) and divided Gilead into two equal parts (Josh 12:2; Judg 11:13–22). It marked the boundary between the kingdom of Og (Bashan) and that of Sihon (Heshbon), as well as the northern frontier of the Ammonites (Num 21:24; Deut 2:37; 3:16. Cf. Flavius Josephus, *Antiquitates Judaicae*, IV, 5, 2–3). It also appears in Judt 2:24 (according to the Peshitta).
Many itineraries place it about 3 km south of the Sea of Huleh, on account of the so-called “Jacob’s bridge”; others locate it 2 or 3 miles south of the Sea of Tiberias; still others confuse it with the Yarmūk. Today it is commonly identified with the Nahr ez-Zerqāʾ (“blue river”), the most important tributary of the Jordan after the Yarmūk. It rises from the ʿAmmān stream (alt. 788 m) west of the city of that name, but its true source (Rās ez-Zerqāʾ) is near Qalʿat ez-Zerqāʾ, where it is joined by the waters of ʿAjn ez-Zerqāʾ. After describing a great arc of 70 km, it empties into the Jordan near the bridge of ed-Damjeh, opposite Qarn Sarjabah. On average it is 16 m wide and 60 cm deep. Its waters are clear and rich in fish; the bed is deeply incised, and the steep banks are picturesque with broom, oleanders, etc. Its tributaries include the Wādi ed-Dlejl, el-Qnejjeh, er-Rijāš, Sejl Āerās, and others.