Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Sa2 8:1-8) David subdues the Philistines, the Moabites, and the Syrians.
(Sa2 8:9-14) The spoil dedicated.
(Sa2 8:15-18) David's government and officers.
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.
All the precious things David was master of, were dedicated things; they were designed for building the temple. The idols of gold David destroyed, Sa2 5:21, but the vessels of gold he dedicated. Thus, in the conquest of a soul by the grace of the Son of David, what stands in opposition to God must be destroyed, every lust must be mortified and crucified, but what may glorify him must be dedicated; thus the property of it is altered. God employs his servants in various ways; some, as David, in spiritual battles; others, as Solomon, in spiritual buildings; and one prepares work for the other, that God may have the glory of all.
David neither did wrong, nor denied or delayed right to any. This speaks his close application to business; also his readiness to admit all addresses and appeals made to him. He had no respect of persons in judgment. Herein he was a type of Christ. To Him let us submit, his friendship let us seek, his service let us count our pleasure, diligently attending to the work he assigns to each of us. David made his sons chief rulers; but all believers, Christ's spiritual seed, are better preferred, for they are made kings and priests to our God, Rev 1:6.