What does 2 Samuel 17:24 mean?

Absalom's coup has pushed David east. As Absalom marched toward Jerusalem, David hurried his servants out (2 Samuel 15:11–14). As Absalom entered Jerusalem, David climbed the Mount of Olives (2 Samuel 15:37; 16:1). And as Absalom planned his attack, David got his people safely over the Jordan River (2 Samuel 17:1–13, 21–22). David's exiles are on the eastern border of the Trans-Jordan tribes; Absalom and his army have just crossed the Jordan. If Absalom had followed Ahithophel's advice to take a smaller force and only kill David, the war would likely be over already (2 Samuel 17:1–4). Fortunately—for David—Absalom accepted Hushai's alternative and waited to gather a larger army (2 Samuel 17:11–14).

While Absalom's forces set up camp, David's people get the help they need. They're met by the son of the former Ammonite king, the man who faithfully cared for Mephibosheth after Jonathan's death, and a rich Israelite who provides good food and soft beds (2 Samuel 17:27–29). They have time to rest and organize before the inevitable battle.

Absalom has set Amasa over his army (2 Samuel 17:25). Amasa is David's nephew and Absalom, Joab, and Abishai's cousin. David will split his fighting men into three groups under Joab and Abishai, as usual, and Ittai, the leader of the Philistine mercenaries who remained faithful to David (2 Samuel 15:18–22; 18:1–2). David, however, will not attend the battle. His men insist on this: the entire point of this conflict is ensuring that David returns to the throne. David submits to their wishes but tells them not to harm Absalom (2 Samuel 18:3–5). Despite all that has happened, David still suffers from his passivity in the face of his evil sons—the very character flaw that inspired Absalom to rebel against him (2 Samuel 13:20–22).