Numbers 21:24-26

24Israel, however, put him to the sword and took over his land from the Arnon to the Jabbok, but only as far as the Ammonites, because their border was fortified. 25Israel captured all the cities of the Amorites and occupied them, including Heshbon and all its surrounding settlements. 26Heshbon was the city of Sihon king of the Amorites, who had fought against the former king of Moab and had taken from him all his land as far as the Arnon.