'Frontier' in the Bible

From there they journeyed on and camped on the other side of [the river] Arnon, which is in the wilderness that extends from the boundary of the Amorites; for [the river] Arnon is the boundary of Moab, between Moab and the Amorites.

It continued along to Azmon and proceeded to the Brook of Egypt (Wadi el-Arish), and the border ended at the [Mediterranean] sea. This was their southern border.

He ruled over all the kings from the Euphrates River to the land of the Philistines, and as far as the border of Egypt.