2 Samuel 3:26-30 - Joab Murders Abner
26 And when Joab was come out from the king, he sent messengers after Abner, which brought him again from the well of Sirah - unwitting to David. 27 And when Abner was come again to Hebron, Joab took him aside in the gate, to speak with him guilefully, and there smote him under the short ribs that he died, for the blood of Asahel his brother.
28 And when it afterward came to David's ear, he said, "I and my kingdom are guiltless before the LORD forever, concerning the blood of Abner the son of Ner. 29 It fall therefore on the head of Joab and on all his father's house: that the house of Joab be never without one or other that hath running issues or without lepers and goers on crutches, and that fall on the sword and that lack bread." 30 And the cause why Joab and Abishai slew Abner was that Abner had slain their brother Asahel at Gibeon in battle.