Shortly after taking the throne, King David directly violated the cultural norm. Historically when a new King took the throne, it was common that he would execute the old king and his family so nobody from that dynasty could rise up against him. We are not saying it's right, but it was fairly common, especially if there was a power struggle leading up to that point. David directly violated this by showing kindness to Mephibosheth, a grandson of King Saul, (the guy that literally hunted David as an animal for years). Humanly speaking David had every right to hate all of Saul's family, but he was good friends with Jonathan, Saul's son. And out of respect for him, and in keeping his promise he showed the world a better way. God’s Way.