As soon as Joab had left David, he sent messengers after Abner, who brought him back from the well of Sirah. But David was unaware of it.
After leaving David, Joab sends messengers to bring Abner back from the well of Sirah, and David does not know it.
It shows Joab acting secretly and outside the king’s knowledge.
22Just then David’s soldiers and Joab returned from a raid, bringing with them a great plunder. But Abner was not with David in Hebron, because David had sent him on his way in peace. 23When Joab and all his troops arrived, he was informed, “Abner son of Ner came to see the king, who sent him on his way in peace.” 24So Joab went to the king and said, “What have you done? Look, Abner came to you. Why did you dismiss him? Now he is getting away! 25Surely you realize that Abner son of Ner came to deceive you and to track your movements and all that you are doing.” 26As soon as Joab had left David, he sent messengers after Abner, who brought him back from the well of Sirah. But David was unaware of it. 27When Abner returned to Hebron, Joab pulled him aside into the gateway, as if to speak to him privately, and there Joab stabbed him in the stomach. So Abner died on account of the blood of Joab’s brother Asahel. 28Afterward, David heard about this and said, “I and my kingdom are forever guiltless before the LORD concerning the blood of Abner son of Ner. 29May it whirl over the head of Joab and over the entire house of his father, and may the house of Joab never be without one having a discharge or skin disease, or one who leans on a staff or falls by the sword or lacks food.” 30(Joab and his brother Abishai murdered Abner because he had killed their brother Asahel in the battle at Gibeon.)