Numbers 34:5

And the border shall fetch a compass... — Although the exact spots of some of the places which determined the southern border have not been positively ascertained, there seems, on the whole, very little doubt that the boundary line ran along the valleys which form a natural division between the cultivated land and the desert, from the Arabah on the east to the Mediterranean on the west, the Brook of Egypt — i.e., the Wady-el-Arish — forming the western boundary until it reached the sea.