The Pulpit Commentary - 2 Samuel 3:31
David said to Joab. The excuse of the blood feud made it impossible for David to punish Joab further than by depriving him of his command; but he made him condemn his own deed by taking part in the public mourning for the man he had murdered. This mourning consisted in going in solemn procession, clad in sackcloth, before Abner's body, carried on a bier to the grave, while David followed as chief mourner; and the emphatic way in which he is called King David suggests the thought that he... read more
Adam Clarke's Commentary on the Bible - 2 Samuel 3:36
The people took notice - They saw that the king's grief was sincere, and that he had no part nor device in the murder of Abner: see 2 Samuel 3:37 . read more