Here is, 1. A new attempt of the Syrians to recover their lost honour and to check the progress of David's victorious arms. The forces that were lately dispersed rallied again, and gathered themselves together, Sa2 10:15. Even the baffled cause will make head as long as there is any life in it; the enemies of the Son of David do so, Matt, Sa2 22:34; Rev 19:19. These, being conscious of their insufficiency, called in the aid of their allies and dependencies on the other side of the river (Sa2 10:16), and, being thus recruited, they hoped to make their part good against Israel, but they knew not the thoughts of the Lord, for he gathered them as sheaves into the floor; see Mic 4:11-13. 2. The defeat of this attempt by the vigilance and valour of David, who, upon notice of their design, resolved not to stay till they attacked him, but went in person at the head of his army over Jordan (Sa2 10:17), and, in a pitched battle, routed the Syrians (Sa2 10:18), slew 7000 men, who belonged to 700 chariots, and 40,000 other soldiers, horse and foot, as appears by comparing Ch1 19:18. Their general was killed in the battle, and David came home in triumph, no doubt. 3. The consequence of this victory over the Syrians. (1.) David gained several tributaries, Sa2 10:19. The kings, or petty princes, that had been subject to Hadarezer, when they saw how powerful David was, very wisely made peace with Israel, whom they found they could not make war with, and served them, since they were able to give them protection. Thus the promise made to Abraham (Gen 15:18), and repeated to Joshua (Jos 1:4), that the borders of Israel should extend to the river Euphrates, was performed, at length. (2.) The Ammonites lost their old allies: The Syrians feared to help the children of Ammon, not because they had an unrighteous cause (justifying a crime which was a breach of the law of nations), but because they found it was an unsuccessful cause. It is dangerous helping those that have God against them; for, when they fall, their helpers will fall with them.
Jesus Christ, the Son of David, sent his ambassadors, his apostles and ministers, after all his servants the prophets, to the Jewish church and nation; but they treated them shamefully, as Hanun did David's ambassadors, mocked them, abused them, slew them; and it was this that filled the measure of their iniquity, and brought upon them ruin without remedy (Mat 21:35, Mat 21:41, Mat 22:7; compare Ch2 26:16); for Christ takes the affronts and injuries done to his ministers as done to himself and will avenge them accordingly.

David - gathered all Israel together - He thought that such a war required his own presence.

And when it was told David,.... What preparations the Syrians were making to fight him, and where they were:

he gathered all Israel together; all the fighting men in the country:

and passed over Jordan, and came to Helam: which, according to Bunting (b), was twenty miles from Jerusalem. David seems to have gone himself in person to this war:

and the Syrians set themselves in array against David, and fought with him; they formed themselves in a line of battle, and attacked him first, being eager to fight, and perhaps confident of victory, because of their numbers.

(b) Travels, &c. p. 140, 141.

THE SYRIANS DEFEATED. (Sa2 10:15-19)

Hadarezer sent and brought out the Syrians that were beyond the river--This prince had enjoyed a breathing time after his defeat (Sa2 8:3). But alarmed at the increasing power and greatness of David, as well as being an ally of the Ammonites, he levied a vast army not only in Syria, but in Mesopotamia, to invade the Hebrew kingdom. Shobach, his general, in pursuance of this design, had marched his troops as far as Kelam, a border town of eastern Manasseh, when David, crossing the Jordan by forced marches, suddenly surprised, defeated, and dispersed them. As a result of this great and decisive victory, all the petty kingdoms of Syria submitted and became his tributaries (see on Ch1 19:1).

Next: 2 Samuel Chapter 11