John Gill Bible Commentary

And all the cities of the plain,.... In the champaign country, as well as those in the mountainous part: and all the kingdom of Sihon; or, as Masius renders the words, "which all had been the kingdom of Sihon"; for the whole kingdom of Sihon was not given to Reuben, only a part of it, and the rest to Gad, as in Jos 13:27, king of the Amorites, which reigned in Heshbon; as in Jos 13:10, whom Moses smote with the princes of Midian, Evi, and Rekem, and Zur, and Hur, and Reba; not at the same time that Sihon was smitten by him, but afterwards in a war with Midian, Num 31:8; where their names are given as here; and there they are called kings of Midian, petty kings, and, as it seems by what follows, were subject to Sihon, and therefore are here mentioned: which were dukes of Sihon dwelling in the country; for Midian, as Kimchi supposes, and not without reason, was under the government of Sihon, and these were his nobles, though they dwelt in the land of Midian.