Assemble me the men of Judah David here made good his promise to Amasa, which was a great encouragement to others in the tribe of Judah to adhere to him. And by this means also the seditious Israelites might be the sooner brought to reason, when they saw their old general in the field against them. He tarried longer than the set time Finding some difficulty in the business, either because the people, being wearied out by the late war, were not forward to engage in another; or because the soldiers had more affection to Joab than to their new general.
Related Commentaries of 2 Samuel 20:4
2 Samuel 20:4-5
4 Then said the king to Amasa, Assembleb me the men of Judah within three days, and be thou here present.
5 So Amasa went to assemble the men of Judah: but he tarried longer than the set time which he had appointed him.