In this passage we see the strength of David and the weakness of David. First, the strength. David was an amazing military leader. Notice his strategy of going through the water shaft to attack Jerusalem. Yet what made him that great military leader was his reliance on God’s guidance when making decisions. His victories over the Philistines were great examples of David following God’s lead.
Yet we also see David’s weakness. In verse 13 it said that he took more concubines and wives from Jerusalem. His unwillingness to live within the one man/one woman relationship that God had desired (even if multiple wives were socially accepted in his time) would be his source of trouble and heartache throughout his reign of king. His model of a family would be taken by his son, Solomon, to an even greater extreme, and would eventually lead to the division of his United Kingdom (Judah and Israel as one nation).
No one is perfect, not even David, a man after God’s own heart. These sins we commit come back to haunt us, as we reap the fruits of those sins. Yet God still forgives us through Christ. He still calls us His own. That’s what grace is all about.