Numbers 21:23-26

23But Sihon would not allow Israel to pass through his territory. So Sihon gathered all his people together and went out against Israel in the wilderness, and he came to Jahaz and fought against Israel.

24Then Israel defeated him with the edge of the sword, and took possession of his land from the Arnon to the Jabbok, as far as the people of Ammon; for the border of the people of Ammon was fortified.

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

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