Joab considered Abner an enemy and so he accused David of wrongdoing in letting him go.1 In the context of a war, the capture and death of Abner would have been a great help to David’s cause, possibly even bringing the civil war to an end. In Joab’s opinion, it would have helped to smooth David’s rise to the throne of all Israel.
24 Then Joab went to the king and said, “What have you done? Behold, Abner came to you. Why is it that you have sent him away, so that he is gone?