Jahaz

trodden down [called also Jahaza, (Josh 13:18); Jahazah, (Josh 21:36); Jahzah, (1Chr 6:78)], a town where Sihon was defeated, in the borders of Moab and in the land of the Ammonites beyond Jordan, and north of the river Arnon (Num 21:23; Deut 2:32). It was situated in the tribe of Reuben, and was assigned to the Merarite Levites (Josh 13:18; 21:36). Here was fought the decisive battle in which Sihon (q.v.) was completely routed, and his territory (the modern Belka) came into the possession of Israel. This town is mentioned in the denunciations of the prophets against Moab (Isa 15:4; Jer 48:34).

EBD - Easton's Bible Dictionary