This rhetorical question is used to warn Asahel of the danger he faced. "Strike to the ground" is a polite way of saying "to kill." AT: "I do not wish to kill you" (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-euphemism]])
This rhetorical question emphasizes that Abner does not want to fight and kill Asahel because it would destroy Abner's relationship with Joab. Here "hold up my face to Joab" is an idiom that means that he would be too ashamed to look at Joab. AT: "I would be too ashamed to look at your brother, Joab" (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-idiom]])