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.

Read Numbers 21:24 Using Other Translations

And Israel smote him with the edge of the sword, and possessed his land from Arnon unto Jabbok, even unto the children of Ammon: for the border of the children of Ammon was strong.
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.
But the Israelites slaughtered them with their swords and occupied their land from the Arnon River to the Jabbok River. They went only as far as the Ammonite border because the boundary of the Ammonites was fortified.