ja'-zer (ya`zer or ya`zeyr; Septuagint Iazen in Codex Alexandrinus; Iazer):
In some cases, e.g. Numbers 21:32, the King James Version reads "Jaazer." This was a city of the Amorites East of the Jordan taken, along with its towns, by Moses, and occupied by the tribe of Gad (Numbers 21:32; 32:35). The country was very fertile, and its spacious pasture-lands attracted the flock-masters of Gad (Numbers 32:1), the southern border of whose territory it marked (Joshua 13:25). It was assigned to the Merarite Levites (Joshua 21:39; 1 Chronicles 6:81). The place was reached by Joab when taking the census (2 Samuel 24:5). In the 40th year of King David mighty men of valor were found here to whom he entrusted the oversight in Reuben and Gad "for every matter pertaining to God, and run the affairs of the king" (1 Chronicles 26:32). The fruitfulness of the country is alluded to in Isaiah 16:8; Jeremiah 48:32. (Note: "Sea of" Jazer in this verse has arisen through accidental repetition of yam, "sea," from the preceding clause.) The city was taken from the Ammonites by Judas Maccabeus, and burned (1 Macc 5:7,8; Ant, XII, viii, 1).
Onomasticon places Jazer 10 Roman miles West of Philadelphia (`Amman), and about 15 miles from Heshbon, where a great stream rises, which flows into the Jordan. Many would identify it with Khirbet Car, on the South of Wady Cir, about 5 miles West of `Amman. The perennial stream from Wady Cir reaches the Jordan by Wady el-Kefrein. Cheyne (EB, under the word) suggests Yajuz on Wady Zorby, tributary of the Jabbok, with extensive Roman remains. It lies a little way to the East of el Jubeihat ("Jogbehah," Numbers 32:35). It is situated, however, to the North and not to the West of `Amman, where Eusebius, Onomasticon, places it. Neither identification is certain.