David had told his troops, “The first soldier to kill a Jebusite will become my army commander.” And since Joab son of Zeruiah attacked first, he became commander.
Meanwhile, Joab the son of Zeruiah was leading David's soldiers, and the two groups met at the pool in Gibeon. Abner and his men sat down on one side of the pool, while Joab and his men sat on the other side.
When Abner returned to Hebron, Joab pretended he wanted to talk privately with him. So he took Abner into one of the small rooms that were part of the town gate and stabbed him in the stomach. Joab killed him because Abner had killed Joab's brother Asahel.
They said to each other, “Look how he keeps coming out to insult us. The king is offering a big reward to the man who kills Goliath. That man will even get to marry the king's daughter, and no one in his family will ever have to pay taxes again.”