Numbers 21:23-26

23But Sihon would not let the Israelites travel through his land. Sihon and his army marched to Jahaz, in the desert. They attacked the Israelites there.

24The Israelites fought against the army of Sihon and they won. They got power over the land from the River Arnon to the River Jabbok. But the border of the Ammonites' land had strong towns, so they could not go beyond them.

25They got power over all the cities of the Amorites. Those cities included Heshbon and the towns round it.

26Heshbon was the city of Sihon, the king of the Amorites. He had fought against the king of Moab. He took from the king of Moab the land as far as the River Arnon.