Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[39] When David heard that Abner was slain, it grieved his soul; and he called all men to witness, with stretching out his hands to God, and crying out that he was not a partaker in the murder of Abner, and that his death was not procured by his command or approbation. He also wished the heaviest curses might light upon him that slew him and upon his whole house; and he devoted those that had assisted him in this murder to the same penalties on its account; for he took care not to appear to have had any hand in this murder, contrary to the assurances he had given and the oaths he had taken to Abner. However, he commanded all the people to weep and lament this man, and to honor his dead body with the usual solemnities; that is, by rending their garments, and putting on sackcloth, and that things should be the habit in which they should go before the bier; after which he followed it himself, with the elders and those that were rulers, lamenting Abner, and by his tears demonstrating his good-will to him while he was alive, and his sorrow for him now he was dead, and that he was not taken off with his consent. So he buried him at Hebron in a magnificent manner, and indited funeral elegies for him; he also stood first over the monument weeping, and caused others to do the same; nay, so deeply did the death of Abner disorder him, that his companions could by no means force him to take any food, but he affirmed with an oath that he would taste nothing till the sun was set. This procedure gained him the good-will of the multitude; for such as had an affection for Abner were mightily satisfied with the respect he paid him when he was dead, and the observation of that faith he had plighted to him, which was shown in his vouchsafing him all the usual ceremonies, as if he had been his kinsman and his friend, and not suffering him to be neglected and injured with a dishonorable burial, as if he had been his enemy; insomuch that the entire nation rejoiced at the king's gentleness and mildness of disposition, every one being ready to suppose that the king would have taken the same care of them in the like circumstances, which they saw be showed in the burial of the dead body of Abner. And indeed David principally intended to gain a good reputation, and therefore he took care to do what was proper in this case, whence none had any suspicion that he was the author of Abner's death. He also said this to the multitude, that he was greatly troubled at the death of so good a man; and that the affairs of the Hebrews had suffered great detriment by being deprived of him, who was of so great abilities to preserve them by his excellent advice, and by the strength of his hands in war. But he added, that "God, who hath a regard to all men's actions, will not suffer this man [Joab] to go off unrevenged; but know ye, that I am not able to do any thing to these sons of Zeruiah, Joab and Abishai, who have more power than I have; but God will requite their insolent attempts upon their own heads." And this was the fatal conclusion of the life of Abner.