When Abner returned to Hebron, Joab took him aside at the gate as if to speak privately with him. Joab then stabbed him in the abdomen and killed him, avenging the shed blood of his brother Asahel. When David later heard about this, he said, "I and my kingdom are forever innocent before the Lord of the shed blood of Abner son of Ner! May his blood whirl over the head of Joab and the entire house of his father! May the males of Joab's house never cease to have someone with a running sore or a skin disease or one who works at the spindle or one who falls by the sword or one who lacks food!" read more.
So Joab and his brother Abishai killed Abner, because he had killed their brother Asahel in Gibeon during the battle. David instructed Joab and all the people who were with him, "Tear your clothes! Put on sackcloth! Lament before Abner!" Now King David followed behind the funeral bier. So they buried Abner in Hebron. The king cried loudly over Abner's grave and all the people wept too. The king chanted the following lament for Abner: "Should Abner have died like a fool? Your hands were not bound, and your feet were not put into irons. You fell the way one falls before criminals." All the people wept over him again. Then all the people came and encouraged David to eat food while it was still day. But David took an oath saying, "God will punish me severely if I taste bread or anything whatsoever before the sun sets!" All the people noticed this and it pleased them. In fact, everything the king did pleased all the people. All the people and all Israel realized on that day that the killing of Abner son of Ner was not done at the king's instigation. Then the king said to his servants, "Do you not realize that a great leader has fallen this day in Israel? Today I am weak, even though I am anointed as king. These men, the sons of Zeruiah, are too much for me to bear! May the Lord punish appropriately the one who has done this evil thing!"