2 Samuel 3:26-30 - Joab Murders Abner
26 And when Joab came out from David, he sent messengers after Abner, and they brought him back from the well of Sirah, but David knew it not. 27 And when Abner was returned to Hebron, Joab took him aside into the midst of the gate to speak with him quietly, and smote him there in the body, so that he died, for the blood of Asahel his brother.
28 And afterward, when David heard it, he said, I and my kingdom are guiltless before LORD forever of the blood of Abner the son of Ner. 29 Let it fall upon the head of Joab, and upon all his father's house. And let there not fail from the house of Joab one who has an issue, or who is a leper, or who leans on a staff, or who falls by the sword, or who lacks bread. 30 So Joab and Abishai his brother killed Abner because he had killed their brother Asahel at Gibeon in the battle.