This chapter is a reflection of II Samuel 8:1-18. There are two outstanding traits about David's life and reign that arise several times in this chapter: 1. the tens of thousands of men who David and his army killed, and 2. the abundance of wealth that David collected. These 2 issues are particularly interesting because of how they seem to run against the grain of our modern Christian sensibilities. In our sterile environment of affluence and self-proclaimed civility, and in light of the New Testament principles of tolerance, world-wide missions, evangelism and compassion, one might find it hard to envision how King David could be so godly and at the same time be collecting tons of gold, silver and brass from the pockets of the massive numbers of gentiles whom he killed in war.
There are a couple of things that we need to remember though. First, David was fighting against ungodly heathen under the auspices and authority of God. God had decreed their judgment and David was simply the executor of it. And, as the head of a sovereign nation David was doing something that even governments today have a God-given right and responsibility to do. He was waging wars against evil threats that existed in the nations around his own. Even today we have no reason to wonder if God is in favor of, or opposed to, war, when the cause is just and right. War is not wicked if it is carried out by [relatively] good nations against evil ones, against legitimate threats, for just causes and to protect innocent people.
Secondly, the collection of wealth for one's own sake and pleasure has been evil in all generations. David wasn't necessarily collecting material wealth to provide safety for himself nor to satiate his own greed, but perhaps to supply adequate materials for the construction of God's house (much like the plundering of Egypt in Moses’ day).