Charles Ellicott Commentary 2 Samuel 17:2

"and I will come upon him while he is weary and weak-handed, and will make him afraid; and all the people that are with him shall flee; and I will smite the king only;" — 2 Samuel 17:2 (ASV)

Will make him afraid. —This translation is hardly strong enough. The thought is that Ahithophel will throw his band into a panic by a sudden night attack, and in the confusion will easily secure the person of the king.