Numbers 21:24

And Israel smote him with the edge of the sword
Slew him and his army, entirely routed them, and got a complete victory over them; God giving them up into their hands, who otherwise were a very strong, powerful, and warlike people; see ( Amos 2:9 )

and possessed his land from Arnon unto Jabbok;
two rivers, the one to the south, the other to the north of his country; the one was the boundary of his country between him and the Moabites, the other the boundary of his country between him and the Ammonites, as it follows:

even unto the children of Ammon; for the border of the children of
Ammon was strong;
which is given as a reason why the Israelites proceeded no further in their conquest; there was another reason for that, which was the order of the Lord not to distress the Ammonites, nor meddle with them; though Jarchi makes this prohibition to be their strength, ( Deuteronomy 2:19 ) , but this is given as a reason why Sihon could not extend his conquests further, because it was so well fortified, either by nature or art, or both, by the river Jabbok, by mountains and frontier towns, and particularly by Rabbah, as the Targum of Jonathan suggests, which was their royal city in later times, and a very strong place; see ( 2 Samuel 12:26 ) .