It proceeded to Azmon, joined the Brook of Egypt, and ended at the Sea. This was their southern border.
KJV
[From thence] it passed toward Azmon, and went out unto the river of Egypt; and the goings out of that coast were at the sea: this shall be your south coast.
ASV
and it passed along to Azmon, and went out at the brook of Egypt; and the goings out of the border were at the sea: this shall be your south border.