2 Samuel 3:26-27

26And when Joab had gone from David’s presence, he sent messengers after Abner, who brought him back from the well of Sirah. But David did not know it.

27Now when Abner had returned to Hebron, Joab took him aside in the gate to speak with him privately, and there stabbed him in the stomach, so that he died for the blood of Asahel his brother.