David bitterly mourned when Abner was slain by Joab. Abner was a commander in Saul's army and had recently joined forces with David. However, Joab, who was David's commander, was still angry with Abner for killing his brother Asahel in battle. Joab tricked Abner into coming to him and then murdered him. When David heard the news of Abner's death, he mourned deeply and cursed Joab for his treachery. David even wrote a lament, which is recorded in 2 Samuel 3:33-34, expressing his sorrow and honoring Abner's bravery.