21 Then Israel sent messengers to Sihon king of the Amorites, saying, 22 “Let me pass through your land. We will not turn aside into field or vineyard. We will not drink the water of a well. We will go by the King's Highway until we have passed through your territory.” 23 But Sihon would not allow Israel to pass through his territory. He gathered all his people together and went out against Israel to the wilderness and came to Jahaz and fought against Israel. 24 And Israel defeated him with the edge of the sword and took possession of his land from the Arnon to the Jabbok, as far as to the Ammonites, for the border of the Ammonites was strong. 25 And Israel took all these cities, and Israel settled in all the cities of the Amorites, in Heshbon, and in all its villages. 26 For Heshbon was the city of Sihon the king of the Amorites, who had fought against the former king of Moab and taken all his land out of his hand, as far as the Arnon. 27 Therefore the ballad singers say,
“Come to Heshbon, let it be built;
let the city of Sihon be established.
28 For fire came out from Heshbon,
flame from the city of Sihon.
It devoured Ar of Moab,
and swallowed  the heights of the Arnon.
29 Woe to you, O Moab!
You are undone, O people of Chemosh!
He has made his sons fugitives,
and his daughters captives,
to an Amorite king, Sihon.
30 So we overthrew them;
Heshbon, as far as Dibon, perished;
and we laid waste as far as Nophah;
fire spread as far as Medeba.” 
31 Thus Israel lived in the land of the Amorites. 32 And Moses sent to spy out Jazer, and they captured its villages and dispossessed the Amorites who were there. 33 Then they turned and went up by the way to Bashan. And Og the king of Bashan came out against them, he and all his people, to battle at Edrei. 34 But the Lord said to Moses, “Do not fear him, for I have given him into your hand, and all his people, and his land. And you shall do to him as you did to Sihon king of the Amorites, who lived at Heshbon.” 35 So they defeated him and his sons and all his people, until he had no survivor left. And they possessed his land. (ESV)