2 Samuel 3:39 - Ellicott's Commentary On The Whole Bible

I am this day weak. — David’s high appreciation of the importance and value of Abner shows that Joab’s jealousy was not without ground, and there is a tone of deep sadness in his words, “these men the sons of Zeruiah be too hard for me.” He knew their ungoverned passions, their bold lawlessness, and at the same time their great power and popularity with the army, and he dared not punish them. He leaves their judgment to God.