יהושע טו:ז פירוש: רש״י

The boundary went up to Devir from the Valley of Ochor. The Valley of Ochor was between Even Bohan and Devir.

And it turned northward to Gilgol. When it reached Gilgol, the boundary widens, and the borderline extends northward to Gilgol which is opposite Maalei-adumim, whose elevation [Maalei] is south of the Valley. The valley therefore is outside the borderline and is not within the boundary of Yehudah.

South of the Valley. It was a steep incline without water.¹⁰נַחַל is usually translated as a river, but since as Rashi comments, there was no water, he translates it as a valley.