David smote also Hadadezer, the son of Rehob, king of Zobah, as he went to recover his border at the river Euphrates.

Wesley's Notes

8:3 As he went - David, remembering the grant which God had made to his people of all the land as far as Euphrates, and having subdued his neighbouring enemies, went to recover his rights, and stablish his dominion as far as Euphrates.

King James Translators' Notes

Hadadezer: or, Hadarezer

Jamieson-Fausset-Brown Bible Commentary

2Sa 8:3-14. He Smites Hadadezer and the Syrians.

3. Zobah-(1Ch 18:3). This kingdom was bounded on the east by the Euphrates, and it extended westward from that river, perhaps as far north as Aleppo. It was long the chief among the petty kingdoms of Syria, and its king bore the hereditary title of "Hadadezer" or "Hadarezer" ("Hadad," that is, "helped").

as he went to recover his border at the river Euphrates-in accordance with the promises God made to Israel that He would give them all the country as far as the Euphrates (Ge 15:18; Nu 24:17). In the first campaign David signally defeated Hadadezer. Besides a great number of foot prisoners, he took from him an immense amount of booty in chariots and horses. Reserving only a small number of the latter, he hamstrung the rest. The horses were thus mutilated because they were forbidden to the Hebrews, both in war and agriculture. So it was of no use to keep them. Besides, their neighbors placed much dependence on cavalry, but having, for want of a native breed, to procure them by purchase, the greatest damage that could be done to such enemies was to render their horses unserviceable in war. (See also Ge 46:6; Jos 11:6, 9). A king of Damascene-Syria came to Hadadezer's succor; but David routed those auxiliary forces also, took possession of their country, put garrisons into their fortified towns, and made them tributary.

Matthew Henry's Concise Commentary

8:1-8. David subdued the Philistines. They had long been troublesome to Israel. And after the long and frequent struggles the saints have with the powers of darkness, like Israel with the Philistines, the Son of David shall tread them all under foot, and make the saints more than conquerors. He smote the Moabites, and made them tributaries to Israel. Two parts he destroyed, the third part he spared. The line that was to keep alive, though it was but one, is ordered to be a full line. Let the line of mercy be stretched to the utmost. He smote the Syrians. In all these wars David was protected, for this in his psalms he often gives glory to God.