The east border was the Salt Sea as far as the mouth of the Jordan. And the border on the northern quarter began at the bay of the sea at the mouth of the Jordan.
Joshua 15:5
Surrounding context
15:4 From there it passed toward Azmon and went out to the Brook of Egypt; and the border ended at the sea. This shall be your southern border.
15:5 The east border was the Salt Sea as far as the mouth of the Jordan. And the border on the northern quarter began at the bay of the sea at the mouth of the Jordan.
15:6 The border went up to Beth Hoglah and passed north of Beth Arabah; and the border went up to the stone of Bohan the son of Reuben.