2 Samuel 3:11

And he could not answer Abner a word again, because he feared him.

Ishbosheth was weak and incompetent, and because he feared Abner he could not answer a word again when Abner became incensed against him. That quarrel overthrew by treachery the throne that malice and ambition had established, for Abner deserted to David with the offer to bring over to him all the tribes of Israel. David accepted his proposals and dismissed him with honor to accomplish his purpose. The favorable reception of so valiant and famed a warrior excited the jealousy of Joab as commander and prospective rival.