יהושע, פרק י״ב, פסוק ב׳

The narrative details the specific territory ruled individually by Sihon, the Amorite king [מלבי״ם]. Governing from his capital city of Heshbon, his authority extended over a vast geographic region. The border of his domain began at the city of Aroer, situated on the banks of the Arnon River. His control was not limited to the riverbank but included the land within the river valley itself, which was a practical and usable area [ביאור שטיינזלץ].

From the Arnon River, Sihon's kingdom expanded to encompass half of the Gilead region. This territory stretched until it reached a settlement situated near the Jabbok River [מצודת דוד]. This location served as a precise boundary marker, as it bordered the land of the Ammonites. Beyond this exact point, Sihon's rule ended, marking the beginning of the exclusive domain of the Ammonites [רש״י].