2 Samuel 3:24-27

24Then Joab came to the king, and said, What hast thou done? behold, Abner came unto thee; why is it that thou hast sent him away, and he is quite gone? 25Thou knowest Abner the son of Ner, that he came to deceive thee, and to know thy going out and thy coming in, and to know all that thou doest. 26And when Joab was come out from David, he sent messengers after Abner, and they brought him back from the well of Sirah: but David knew it not.

27And 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.