Commentaire sur Les Nombres 34:3

והיה לכם פאת נגב THE SOUTHERN פאה SHALL BE UNTO YOU — i.e. the south side which extends from east to west (פאה does not here mean “corner”).

על ידי אדום, close to Edom.

והיה לכם פאת נגב ממדבר צן על ידי אדום, “Your southernmost point shall be from the edge of the Wilderness of Tzin, at the side of Edom.” The word על יד means the same as אצל, “next to.” We also find this expression in Numbers 13,9. The purpose of this whole list is to tell the Israelites the part of the country they were obligated to conquer. Rashi comments that this is extremely important as there are many commandments in the Torah which are applicable only within the boundaries delineated by the Torah in this chapter. It was critical therefore to know these details precisely.