2 Samuel 3:24-27

24Then Joab came to the king and said, “What have you done? Look here, Abner came to you—why did you send him away? Now he is getting away!

25You know Abner son of Ner—surely he came to deceive you, to spy on your goings and comings, and to find out all that you are doing.”

26When Joab left David, he sent messengers after Abner, so they brought him back from the well of Sirah, though David knew nothing about it.

27Now when Abner returned to Hebron, Joab took him aside within the gate to speak with him privately, and there stabbed him in the groin, so that he died—on account of the blood of his brother Asahel.