1 Samuel 14:50 (ESV)

50 And the name of Saul’s wife was Ahinoam the daughter of Ahimaaz. And the name of the commander of his army was Abner the son of Ner, Saul’s uncle.

Abner was commander of Saul’s army (1 Samuel 12:9; 2 Samuel 2:8). During the brief reign of Ishbaal (2 Samuel 2:8–10), he held great power until he was slain by Joab the commander of David’s army (2 Samuel 3:27).1