25 You know that Abner the son of Ner came to deceive you, and to know your going out and your coming in, and to know all that you are doing." 26 When Jo'ab came out from David's presence, he sent messengers after Abner, and they brought him back from the cistern of Sirah; but David did not know about it. 27 And when Abner returned to Hebron, Jo'ab took him aside into the midst of the gate to speak with him privately, and there he smote him in the belly, so that he died, for the blood of As'ahel his brother. 28 Afterward, when David heard of it, he said, "I and my kingdom are for ever guiltless before the Lord for the blood of Abner the son of Ner. 29 May it fall upon the head of Jo'ab, and upon all his father's house; and may the house of Jo'ab never be without one who has a discharge, or who is leprous, or who holds a spindle, or who is slain by the sword, or who lacks bread!" 30 So Jo'ab and Abi'shai his brother slew Abner, because he had killed their brother As'ahel in the battle at Gibeon. 31 Then David said to Jo'ab and to all the people who were with him, "Rend your clothes, and gird on sackcloth, and mourn before Abner." And King David followed the bier. 32 They buried Abner at Hebron; and the king lifted up his voice and wept at the grave of Abner; and all the people wept. 33 And the king lamented for Abner, saying, "Should Abner die as a fool dies? 34 Your hands were not bound, your feet were not fettered; as one falls before the wicked you have fallen." And all the people wept again over him. 35 Then all the people came to persuade David to eat bread while it was yet day; but David swore, saying, "God do so to me and more also, if I taste bread or anything else till the sun goes down!"
Matthew Henry's Commentary on 2 Samuel 3:25-35
Commentary on 2 Samuel 3:22-39
(Read 2 Samuel 3:22-39)
Judgments are prepared for such scorners as Abner; but Joab, in what he did, acted wickedly. David laid Abner's murder deeply to heart, and in many ways expressed his detestation of it. The guilt of blood brings a curse upon families: if men do not avenge it, God will. It is a sad thing to die like a fool, as they do that any way shorten their own days, and those who make no provision for another world. Who would be fond of power, when a man may have the name of it, and must be accountable for it, yet is hampered in the use of it? David ought to have done his duty, and then trusted God with the issue. Carnal policy spared Joab. The Son of David may long delay, but never fails to punish impenitent sinners. He who now reigns upon the throne of David, has a kingdom of a nobler kind. Whatever He doeth, is noticed by all his willing people, and is pleasing to them.