Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary
The Eastern Boundary. - If we endeavour to trace the upper line of the eastern boundary from the fountain-place just mentioned, it ran from Hazar-enan to Shepham, the site of which is unknown, and "from Shepham it was to go down to Riblah, on the east of Ain" (the fountain). The article הרבלה, and still more the precise description, "to the east of Ain, the fountain, or fountain locality" (Knobel), show plainly that this Riblah is to be distinguished from the Riblah in the land of Hamath (Kg2 23:33; Kg2 25:21; Jer 39:9; Jer 52:27), with which it is mostly identified. Ain is supposed to be "the great fountain of Neba Anjar, at the foot of Antilibanus, which is often called Birket Anjar, on account of its taking its rise in a small reservoir or pool" (Robinson, Bibl. Res. p. 498), and near to which Mej-del-Anjar is to be seen, consisting of "the ruins of the walls and towers of a fortified town, or rather of a large citadel" (Robinson, p. 496; cf. Ritter, xvii. pp. 181ff.).
(Note: Knobel regards Ain as the source of the Orontes, i.e., Neba Lebweh, and yet, notwithstanding this, identifies Riblah with the village of Ribleh mentioned above. But can this Ribleh, which is at least eight hours to the north of Neba Lebweh, be described as on the east of Ain, i.e., Neba Lebweh?)
From this point the boundary went farther down, and pressed (מחה) "upon the shoulder of the lake of Chinnereth towards the east," i.e., upon the north-east shore of the Sea of Galilee (see Jos 19:35). Hence it ran down along the Jordan to the Salt Sea (Dead Sea). According to these statements, therefore, the eastern boundary went from Bekaa along the western slopes of Antilibanus, over or past Rasbeya and Banyas, at the foot of Hermon, along the edge of the mountains which bound the Huleh basin towards the east, down to the north-east corner of the Sea of Galilee; so that Hermon itself (Jebel es Sheikh) did not belong to the land of Israel.
Jamieson-Fausset-Brown Bible Commentary
east border--This is very clearly defined. Shepham and Riblah, which were in the valley of Lebanon, are mentioned as the boundary line, which commenced a little higher than the sources of the Jordan. Ain is supposed to be the source of that river; and thence the eastern boundary extended along the Jordan, the sea of Chinnereth (Lake of Tiberias), the Jordan; and again terminated at the Dead Sea. The line being drawn on the east of the river and the seas included those waters within the territory of the western tribes.
John Gill Bible Commentary
And ye shall point out your east border from Hazarenan to Shepham. From the place where the northern border ended, which Jerom says (u) the Hebrews call Apamia, as both the Targums of Jonathan and Jerusalem do here. Shepham was a city between Hazarenan and Riblah in the tribe of Naphtali, where Adrichomius (w) places it.
(u) Comment. ut supra. (cf. ver. 15.) (w) Theatrum Terrae Sanct. p. 114.