Joab killed Abner to avenge the death of his brother Asahel (see 2 Samuel 2:18–23). In doing so he committed a sinister form of treachery as he used the name and goodwill of David to lure Abner back to Hebron and then do evil.1 Though he sought to avenge the death of Asahel, he likely also considered Abner to be a rival best gotten rid of.2 The fact that he killed him in Hebron, a city of refuge, only adds to the evil of his deed. Cities of refuge were meant to be a place where due process of law was followed (see Joshua 21:13; Numbers 35:24–25).3
27 Lorsque Abner fut de retour à Hébron, Joab le tira à l'écart au milieu de la porte, comme pour lui parler en secret, et là il le frappa au ventre et le tua, pour venger la mort d'Asaël, son frère.