2 Samuel 3:26-28 Holman Christian Standard Bible (HCSB)
26 Then Joab left David and sent messengers after Abner. They brought him back from the well[a] of Sirah, but David was unaware of it. 27 When Abner returned to Hebron, Joab pulled him aside to the middle of the gateway, as if to speak to him privately, and there Joab stabbed him in the stomach. So Abner died in revenge for the death of Asahel,[b] Joab’s brother.
28 David heard about it later and said: “I and my kingdom are forever innocent before the Lord concerning the blood of Abner son of Ner.