Complete Commentary on the Whole Bible, by Matthew Henry, [1706], at sacred-texts.com
The story is here repeated of David's war with the Ammonites and the Syrians their allies, and the victories he obtained over them, which we read just as it is here related, 2 Sa. 10. Here is, I. David's civility to the king of Ammon, in sending an embassy of condolence to him on occasion of his father's death (Ch1 19:1, Ch1 19:2). II. His great incivility to David, in the base usage he gave to his ambassadors (Ch1 19:3, Ch1 19:4). III. David's just resentment of it, and the war which broke out thereupon, in which the Ammonites acted with policy in bringing the Syrians to their assistance (Ch1 19:6, Ch1 19:7), Joab did bravely (Ch1 19:8-13), and Israel was once and again victorious (Ch1 19:14-19).
Let us here observe, 1. That is becomes good people to be neighbourly, and especially to be grateful. David will pay respect to Hanun because he is his neighbour; and religion teaches us to be civil and obliging to all, to honour all men, and to be ready to do all offices of kindness to those we live among; nor must difference in religion be any obstruction to this. But, besides this, David remembered the kindness which his father showed to him. Those that have received kindness must return it as they have ability and opportunity: those that have received it from the parents must return it to the children when they are gone. 2. That, as saith the proverb of the ancients, Wickedness proceedeth from the wicked, Sa1 24:13. The vile person will speak villany, and the instruments of the churl will be evil, to destroy those with lying words that speak right, Isa 32:6, Isa 32:7. Those that are base, and design ill themselves, are apt to be jealous and to suspect ill of others without cause. Hanun's servant suggested that David's ambassadors came as spies, as if so great and mighty a man as David needed to do so mean a thing (if he had any design upon the Ammonites, he could effect it by open force, and had no occasion for any fraudulent practices), or as if a man of such virtue and honour would do so base a thing. Yet Hanun hearkened to the suggestion, and, against the law of nations, treated David's ambassadors villainously. 3. Masters ought to protect their servants, and with the greatest tenderness to concern themselves for them if they come by any loss or damage in their service. David did so for his ambassadors, Ch1 19:5. Christ will do so for his ministers; and let all masters thus give unto their servants that which is just and equal.
We may see here, 1. How the hearts of sinners that are marked for ruin are hardened to their destruction. The children of Ammon saw that they had made themselves odious to David (Ch1 19:6), and then it would have been their wisdom to desire conditions of peace, to humble themselves and offer any satisfaction for the injury they had done him, the rather because they had made themselves not only odious to David, but obnoxious to the justice of God, who is King of nations, and will assert the injured rights and maintain the violated laws of nations. But, instead of this, they prepared for war, and so brought upon themselves, by David's hand, those desolations which he never intended them. 2. How the courage of brave men is heightened and invigorated by difficulties. When Joab saw that the battle was set against him before and behind (Ch1 19:10), instead of meditating a retreat, he doubled his resolution; and, though he could not double, he divided his army, and not only spoke, but acted, like a gallant man, that had great presence of mind when he saw himself surrounded. He engaged with his brother for mutual assistance (Ch1 19:12), excited himself and the rest of the officers to act vigorously in their respective posts, with an eye to God's glory and their country's good, not to any honour and advantage of their own, and then left the issue to God: Let the Lord do that which is right in his sight. 3. How vain the greatest art and strength are against justice and equity. The Ammonites did their utmost to make the best of their position: they brought as good a force into the field, and disposed it with as much policy as possible; yet, having a bad cause, and acting in defence of wrong, it would not do; they were put to the worst. Right will prevail and triumph at last. 4. To how little purpose it is for those to rally again, and reinforce themselves, that have not God on their side. The Syrians, though in no way concerned in the merits of the cause, but serving only as mercenaries to the Ammonites, when they were beaten, thought themselves concerned to retrieve their honour, and therefore called in the assistance of the Syrians on the other side Euphrates; but to no purpose, for still they fled before Israel (Ch1 19:18); they lost 7000 men, who are said to be the men of 700 chariots, Sa2 10:18. For, as now in a man of war for sea-service they allot ten men to a gun, so then, in land-service, ten men to a chariot. 5. those who have meddled with strife that belongs not to them, and have found that they meddled to their own heart, do well to learn wit at length and meddle no further. The Syrians, finding that Israel was the conquering side, not only broke off their alliance with the Ammonites and would help them no more (Ch1 19:19), but made peace with David and became his servants. Let those who have in vain stood it out against God be thus wise for themselves, and agree with him quickly, while they are in the way. Let them become his servants; for they cannot but see themselves undone if they be his enemies.