2 Samuel 3:15

And Ish-bosheth sent, and took her from her husband, even from Phaltiel the son of Laish.

This moment belongs to the overthrow by treachery of the throne that malice and ambition had established. Abner became incensed against the weak and incompetent Ishbosheth and deserted to David with the offer to bring over all the tribes of Israel to him. David accepted Abner's proposals and then dismissed him with honor to accomplish his purpose.

Abner's favorable reception as a valiant and famed warrior excited the jealousy of Joab, the commander-in-chief of David's army. Joab had a blood-feud with Abner because Abner had slain Asahel, Joab's brother, during the war between Israel and Judah. Seeing an opportunity to avenge his brother's death and rid himself of a prospective rival, Joab basely waylaid and murdered Abner.