Afterward, when David heard it, he said, “My kingdom and I are guiltless before the Lord forever of the blood of Abner the son of Ner. Let it rest on the head of Joab and on all his father’s house; and let there never fail to be in the house of Joab one who has a discharge or is a leper, who leans on a staff or falls by the sword, or who lacks bread.” So Joab and Abishai his brother killed Abner, because he had killed their brother Asahel at Gibeon in the battle.
Then David said to Joab and to all the people who were with him, “Tear your clothes, gird yourselves with sackcloth, and mourn for Abner.” And King David followed the coffin. So they buried Abner in Hebron; and the king lifted up his voice and wept at the grave of Abner, and all the people wept. And the king sang a lament over Abner and said:
“Should Abner die as a fool dies?
Your hands were not bound
Nor your feet put into fetters;
As a man falls before wicked men, so you fell.”
Then all the people wept over him again.
And when all the people came to persuade David to eat food while it was still day, David took an oath, saying, “God do so to me, and more also, if I taste bread or anything else till the sun goes down!” Now all the people took note of it, and it pleased them, since whatever the king did pleased all the people. For all the people and all Israel understood that day that it had not been the king’s intent to kill Abner the son of Ner. Then the king said to his servants, “Do you not know that a prince and a great man has fallen this day in Israel? And I am weak today, though anointed king; and these men, the sons of Zeruiah, are too harsh for me. The Lord shall repay the evildoer according to his wickedness.”
When Saul’s son heard that Abner had died in Hebron, he lost heart, and all Israel was troubled. Now Saul’s son had two men who were captains of troops. The name of one was Baanah and the name of the other Rechab, the sons of Rimmon the Beerothite, of the children of Benjamin. (For Beeroth also was part of Benjamin, because the Beerothites fled to Gittaim and have been sojourners there until this day.)
Jonathan, Saul’s son, had a son who was lame in his feet. He was five years old when the news about Saul and Jonathan came from Jezreel; and his nurse took him up and fled. And it happened, as she made haste to flee, that he fell and became lame. His name was Mephibosheth.
Then the sons of Rimmon the Beerothite, Rechab and Baanah, set out and came at about the heat of the day to the house of Ishbosheth, who was lying on his bed at noon. And they came there, all the way into the house, as though to get wheat, and they stabbed him in the stomach. Then Rechab and Baanah his brother escaped. For when they came into the house, he was lying on his bed in his bedroom; then they struck him and killed him, beheaded him and took his head, and were all night escaping through the plain. And they brought the head of Ishbosheth to David at Hebron, and said to the king, “Here is the head of Ishbosheth, the son of Saul your enemy, who sought your life; and the Lord has avenged my lord the king this day of Saul and his descendants.”
But David answered Rechab and Baanah his brother, the sons of Rimmon the Beerothite, and said to them, “As the Lord lives, who has redeemed my life from all adversity, when someone told me, saying, ‘Look, Saul is dead,’ thinking to have brought good news, I arrested him and had him executed in Ziklag—the one who thought I would give him a reward for his news. How much more, when wicked men have killed a righteous person in his own house on his bed? Therefore, shall I not now require his blood at your hand and remove you from the earth?” So David commanded his young men, and they executed them, cut off their hands and feet, and hanged them by the pool in Hebron. But they took the head of Ishbosheth and buried it in the tomb of Abner in Hebron.
-2 Samuel 3:28-4:12 (NKJV)