Numbers 21:24-26

24But the Israelites defeated him in battle and took possession of his land from the Arnon to the Jabbok, as far as the Ammonites, for the border of the Ammonites was strongly defended.

25So Israel took all these cities; and Israel settled in all the cities of the Amorites, in Heshbon, and in all its villages.

26For Heshbon was the city of King Sihon of the Amorites. Now he had fought against the former king of Moab and had taken all of his land from his control, as far as the Arnon.