'Southern' in the Bible

Their southern border began at the tip of the Dead Sea on the south bay

It proceeded to Azmon and to the Brook of Egypt and so the border ended at the Mediterranean Sea. This is your southern border.

From there the border ascended the Valley of Hinnom to the southern Jebusite slope (that is, Jerusalem) and ascended to the top of the hill that faces the Valley of Hinnom on the west, at the northern end of the Valley of Rephaim.

From there the border went toward Luz, to the southern slope of Luz (that is, Bethel); it then went down by Ataroth-addar, over the hill south of Lower Beth-horon.

The border continued to the north slope of Beth-hoglah and ended at the northern bay of the Dead Sea, at the southern end of the Jordan. This was the southern border.