2 Samuel 3:22-27

And behold, the servants of David and Joab came from a raid and brought much spoil with them; but Abner was not with David in Hebron, for he had sent him away, and he had gone in peace. When Joab and all the army that was with him arrived, they told Joab, saying, “Abner the son of Ner came to the king, and he has sent him away, and he has gone in peace.” Then Joab came to the king and said, “What have you done? Behold, Abner came to you; why then have you sent him away and he is already gone? You know Abner the son of Ner, that he came to deceive you and to learn of your going out and coming in and to find out all that you are doing.” When Joab came out from David, he sent messengers after Abner, and they brought him back from the well of Sirah; but David did not know it. So when Abner returned to Hebron, Joab took him aside into the middle of the gate to speak with him privately, and there he struck him in the belly so that he died on account of the blood of Asahel his brother.