C. F. Keil and Franz Delitzsch on Judges 21:9

Jdg 21:9

In order, however, to confirm the correctness of this answer, which might possibly have been founded upon a superficial and erroneous observation, the whole of the (assembled) people were mustered, and not one of the inhabitants of Jabesh was found there (in the national assembly at Bethel). The situation of Jabesh in Gilead has not yet been ascertained. This town was closely besieged by the Ammonite Nahash, and was relieved by Saul (1Sa 11:1.), on which account the inhabitants afterwards showed themselves grateful to Saul (1Sa 31:8.). Josephus calls Jabesh the metropolis of Gilead (Ant. vi. 5, 1). According to the Onom. (s. v. Jabis), it was six Roman miles from Pella, upon the top of a mountain towards Gerasa. Robinson (Bibl. Res. p. 320) supposes it to be the ruins of ed Deir in the Wady Jabes.