A famine then broke out in Israel.  God told David it was because early in Saul's reign, Saul had tried to annihilate the Gibeonites.  Saul had done this even though Israel had sworn to protect the Gibeonites.  So David allowed some surviving Gibeonites to take revenge on the house of Saul, by killing seven of his grandsons (none were Prince Jonathan's sons as King David had sworn to protect them).  A relative of the seven slain men named Rizpah put out a sackcloth for herself.  Rizpah's sackcloth gave her a place to kneel while she protected the bodies of the slain men from birds and beasts.  David found out that the men hadn't been buried and had them buried.  Then the famine ended.