Joshua 18:14-15

14Then the border extended around the west side to the south, from the hill that lies before Beth Horon southward; and it ended at Kirjath Baal (which is Kirjath Jearim), a city of the children of Judah. This was the west side.

15The south side began at the end of Kirjath Jearim, and the border extended on the west and went out to the spring of the waters of Nephtoah.