Numbers 21:23-26; Numbers 21:34

23 But Sihon would not let Israel pass through his territory. He mustered his entire army and marched out into the wilderness against Israel. When he reached Jahaz, he fought with Israel.

24 Israel, 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.

25 Israel captured all the cities of the Amorites and occupied them, including Heshbon and all its surrounding settlements.

26 Heshbon 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.

34 The LORD said to Moses, “Do not be afraid of him, for I have delivered him into your hands, along with his whole army and his land. Do to him what you did to Sihon king of the Amorites, who reigned in Heshbon.”