וְעָבַ֣ר עַצְמ֗וֹנָה וְיָצָא֙ נַ֣חַל מִצְרַ֔יִם והיה [וְהָי֛וּ] תֹּצְא֥וֹת הַגְּב֖וּל יָ֑מָּה זֶה־יִהְיֶ֥ה לָכֶ֖ם גְּב֥וּל נֶֽגֶב׃
passait par Açmôn, aboutissait au torrent d’Égypte et avait pour limite la mer: "Telle sera pour vous la frontière méridionale."
Rashi
“Your left side” symbolizes Samaria; “your right side” symbolizes Judah, because Judah is in the south of the land of Israel, as it is said (16:46): “And your big sister Samaria...who lives at your left.” Also in the Book of Joshua (15:1), he describes the border of the tribe of Judah as occupying the entire southern border.