Abner knew that Asahel was the brother of Joab and that a fight with him would damage his relationship with Joab.1 He would not be able to engage in diplomacy with Joab if he had killed Joab's brother,2 and he was confident that this would be the outcome of any confrontation. Quite possibly, he sought to keep his options open so that he could defect to David if his plans for Ish-Bosheth did not work out.3
22 And Abner said again to Asahel, “Turn aside from following me. Why should I strike you to the ground? How then could I lift up my face to your brother Joab?”