Numbers 21:21-22:1
Israel now sent messengers to Sihon king of the Amorites, saying, "Let me pass through your country. We will not turn off into fields or vineyards, and we will not drink water from wells. We will follow the king's highway until we have crossed your territory." But Sihon would not let Israel pass through his territory. Sihon gathered all his people and went out against Israel in the wilderness. He came to Jahaz and engaged Israel in battle. But Israel put them to the sword, and took possession of their land, from the Arnon to the Jabbok, as far as [Az] of the Ammonites, for Az marked the boundary of the Ammonites. Israel took all those towns. And Israel settled in all the towns of the Amorites, in Heshbon and all its dependencies.
Now Heshbon was the city of Sihon king of the Amorites, who had fought against a former king of Moab and taken all his land from him as far as the Arnon. Therefore the bards would recite:
"Come to Heshbon; firmly built
And well founded is Sihon's city.
For fire went forth from Heshbon,
Flame from Sihon's city,
Consuming Ar of Moab,
The lords of Bamoth by the Arnon.
Woe to you, O Moab!
You are undone, O people of Chemosh!
His sons are rendered fugitive
And his daughters captive
By an Amorite king, Sihon."
Yet we have cast them down utterly,
Heshbon along with Dibon;
We have wrought desolation at Nophah,
Which is hard by Medeba.
So Israel occupied the land of the Amorites. Then Moses sent to spy out Jazer, and they captured its dependencies and dispossessed the Amorites who were there.
They marched on and went up the road to Bashan, and King Og of Bashan, with all his people, came out to Edrei to engage them in battle. But the Lord said to Moses, "Do not fear him, for I give him and all his people and his land into your hand. You shall do to him as you did to Sihon king of the Amorites who dwelt in Heshbon." They defeated him and his sons and all his people, until no remnant was left him; and they took possession of his country.
The Israelites then marched on and encamped in the steppes of Moab, across the Jordan from Jericho.