Numbers 21:24-26

24Israel struck him with the sword and took possession of his land from the Arnon to the Jabbok, but only up to the Ammonite border, because it was fortified.

25Israel took all the cities and lived in all these Amorite cities, including Heshbon and all its surrounding villages.

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