יהושע, פרק ט״ו, פסוק י׳

The border of the Tribe of Judah winds through the land, carefully circling cities and mountains to define the exact limits of the tribe's territory. As the boundary line reaches Baalah, it shifts direction. The primary approach among commentators is that the path turns west [מצודת דוד, ביאור שטיינזלץ], bringing the border back to its original east-to-west course [רש״י]. Alternatively, this shift might not refer to a western direction, but rather to an actual body of water located south and east of Baalah. From this sea, the boundary makes a sharp turn toward the mountain [מלבי״ם].

The path then reaches Mount Seir. This specific location is a spur of the Judean mountain range that touches the Edomite Mount Seir on its southern edge and shares its name [מלבי״ם]. Moving forward, the border skirts the northern edge of Mount Jearim, also known as Chesalon. By passing to the north, the boundary ensures that the mountain itself falls entirely within the territory of Judah [רש״י, מצודת דוד]. It is necessary to distinguish this location from a similarly named city, Chesil, which was situated in the southern Negev region and eventually given to the Tribe of Simeon [מלבי״ם].

Finally, the border descends to the city of Beth-shemesh and passes by Timnah, placing both locations firmly within Judah's borders. Establishing the exact placement of Beth-shemesh is particularly important to prevent confusion, as other cities shared this exact name in the territories of the tribes of Issachar and Naphtali [מלבי״ם].