Then Nathan said to the king, "Go, do all that is in your heart, for the Lord is with you.", (1 Samuel 7:3)
The obvious isn't always right. The prophet Nathan was a godly man who saw the righteousness of David; thus he assumed that whatever was on David's heart to do was good. It was obvious that the Lord had blessed David's reign as king. Therefore if he desired to build a house for the Lord, surely it was the right thing to do. Well, as we know, it was not. God had another plan, Samuel, David's son was to build the temple of the Lord. David was to supply the resources for him to do so. David was a warrior, a man of blood. He was not to build the temple. The lesson is manifold: never be presumptuous even about the seemingly obvious. Secondly, be prepared to pass the leadership on to another. Thirdly, be ready to meet the need through resources and guidance. And finally, seek and trust the Lord for the final call.