Abner was the son of Ner, commander of Saul’s army. Perhaps a key word to associate with Abner, Saul’s commander, would be unpredictable. He must have been an able warrior to some extent, for he continued to be Saul’s commander throughout Saul’s reign. But even his service to Saul seemed to have some shortcomings.
He was unable to effectively respond to the challenge of the Philistine giant Goliath until the boy David stepped up to help (1 Samuel 17). He also failed to watch over King Saul’s life during the night when David and Abishai infiltrated their camp (1 Samuel 26).
Abner was also somewhat unpredictable after King Saul died. Abner himself was the one who set up Saul’s son Ish-bosheth as king :
Meanwhile, Abner son of Ner, the commander of Saul’s army, had taken Ish-Bosheth son of Saul and brought him over to Mahanaim. He made him king over Gilead, Ashuri and Jezreel, and also over Ephraim, Benjamin and all Israel.(2 Samuel 2:8–9),
but it appears he had aspirations of his own for the throne:
During the war between the house of Saul and the house of David, Abner had been strengthening his own position in the house of Saul.(2 Samuel 3:6).
When Ish-bosheth confronted him about this, Abner responded in anger and threatened to hand the kingdom over to David. Soon after this he did just that.
In the end, Abner fell victim to something he himself did not predict: death at the hands of Joab and Abishai for killing their brother, Asahel. Joab sent messengers to bring Abner to the gates of Hebron as though they had some private matter to discuss, and the two brothers killed him there.
Abner’s death presented a dilemma for David, for it would have looked to many as though David himself had had him killed. To set the record straight, David had Abner buried in full honors and even wept aloud at his funeral (2 Samuel 3:28–39).