John Wesley on Numbers 21:29

People of Chemosh - The worshippers of Chemosh: so the God of the Moabites was called. He, that is, their God, hath delivered up his own people to his and their enemies; nor could he secure even those that had escaped the sword, but suffered them to be carried into captivity. The words of this and the following verse seem to be not a part of that triumphant song made, by some Amoritish poet, which seems to be concluded, Nu 21:28, but of the Israelites making their observation upon it. And here they scoff at the impotency not only of the Moabites, but of their God also, who could not save his people from the sword of Sihon and the Amorites.