From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

Hebrew; Jaezzeer . A town E. of Jordan in Gilead ( Numbers 32:1;  Numbers 32:3-35;  1 Chronicles 26:31). Taken by Israel from the Amorites on the way to Bashan ( Numbers 21:32;  Numbers 21:33). Now the ruins es Szir, ten miles N.E. of Heshbon; a castle and a large walled pool, the "sea" of  Jeremiah 48:32; but Septuagint reads "the cities of Jaazer". Some error may be in the present text. The town gave its name to the surrounding district ( Joshua 13:25;  2 Samuel 24:5). This conquest completed their acquisition of the Amorite kingdom. Soon after, Gad occupied it pastorally. Assigned to the Merarite Levites ( Joshua 21:39), but occupied by Hebronites (Kohathites) in David's time ( 1 Chronicles 26:31).

The plants of the Sibmah vine are said in  Isaiah 16:8 to have come even unto Jaazer, 15 miles from Heshbon, near Sibmah, "they wandered through the wilderness in wild luxuriance," namely, that encompassing Moab, "they are gone over the sea," namely, the sea of Jaazer, but others the Dead Sea ( Psalms 80:8-11). The vine spread itself round the margin of the sea, and reached beyond to the other side; a sad contrast to the coming desolation, when "the pagan lords" should "break down the principal plants"! "Therefore I will weep with the weeping of Jaazer," i.e. such as Jaazer weeps with. Isaiah is touched with pity for Moab, though an alien. Ministers, in denouncing God's wrath against sinners, should do it with tender sorrow, not exultation. At Jaazer was the source of a river falling into Jordan, and marshes or pools still at times are at the source of the wady Szir.

Easton's Bible Dictionary [2]

 Numbers 32:1,35 Joshua 13:25 1 Chronicles 26:31 Isaiah 16:8,9 Jeremiah 48:32

Holman Bible Dictionary [3]

 Numbers 21:32 Numbers 32:35Jazer

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [4]

Khurbet Sar, the probable representative of this locality, is laid down at seven miles west of Amman, with notes of a pool, tower, and sarcophagi adjoining, on the reduced Map of the Ordnance Survey in the fragment published east of the Jordan; but the Memoirs containing details have not appeared. It is situated on the road running along the south side of Wady Sir. Tristram says (Bible Places, page 337): "It consists only of grass- grown mounds and rows of foundations at the very head of the valley, above a marshy spring, the highest source of the Seir." Merrill says (East of the Jordan, page 405), "Sar we made to be 3400 feet above the sea-level;" the Map indicates 1390 feet.

International Standard Bible Encyclopedia [5]

jā´a - zẽr ( יעזיר , ya‛ăzēr ). See Jazer .