Joab asks this question to rebuke David for letting Abner go in peace. Alternate translation: "You should not have done this!" (See: [[rc://en/ta/man/translate/figs-rquestion]])
Joab asks this question to rebuke David for letting Abner escape. This can be translated as a statement. Alternate translation: "Abner was here and you let him leave!" (See: [[rc://en/ta/man/translate/figs-rquestion]])