John Gill's Exposition of the Whole Bible
Numbers 21:28
For there is a fire gone out of Heshbon,.... Not before, but after Sihon had subdued it, as Jarchi observes; and is to be understood of his soldiers going out from thence, and making desolations in the adjacent parts, like a strong fire, and the fierce flames of it there is no resisting; and so the Jerusalem Targum,
"for a people mighty, and burning like fire, are gone out of Heshbon:''
see Amos 1:4: a flame from the city of Sihon: which is the same thing in other words, the city of Sihon being Heshbon, and a flame the same with fire; warriors, as both the Targums of Oakelos and Jerusalem interpret it; this seems to be what those composers undertook in their poetical way to foretell would be the case in future times; concluding, from the conquests already made, that they would be extended much further, and that no opposition could hinder:
it hath consumed Ar of Moab; the metropolis of the country of Moab, that is, they were as sure of it, and endeavoured to make the people by these their compositions as confident of it, that this city would fall into the hands of their armies, and be destroyed, as if it was already done; otherwise it does not appear that it ever was taken out of the hands of the Moabites, until taken by the Assyrians or Chaldeans; of this city Isaiah 15:1
and the lords of the high places of Arnon; who had the government of the high, strong, and fortified places all along the river Arnon; these it is suggested would be conquered by the Amorites; all the three Targums interpret it of the priests and worshippers in the temples, and at the altars of the idols in Arnon; and it may be rendered, "the Baals of the high places of Arnon", as if the gods of those places should fall into the victors' hands; and which seems to have some confirmation from what follows; and it may be observed, that in these parts there were some places called Bamoth Baal, or the high places of Baal, see
Numbers 22:41, and Beth Baal Meon, which has its name from its being the temple and habitation of Baal, Joshua 13:17.