John Gill Bible Commentary

And afterward, when David heard it,.... That Joab had sent to fetch Abner back, and that he had stabbed him in the gate of the city, and he was dead; it was some time after it was done that the news of it was brought to David; this circumstance is observed, the more to clear the king from any concern in this affair: he said; in a public manner, in open court, before all his princes; he called God to witness, and, as Josephus (i) says, stretching out his right hand to God, he cried aloud: I and my kingdom are guiltless before the Lord for ever from the blood of Abner the son of Ner; he was sensible it would be known that Abner had been with him, and that Joab his general had killed him; and therefore it might be suspected that he had an hand in it, and that it was done by his order, with his privy council; and therefore, to purge him and them from it, he made this public declaration, that neither he nor his council knew anything of it; and that it was not done with their knowledge and consent, and by their order, but through the resentment of a single person; and therefore hoped that no man would impute the shedding of this blood unto them, or that God would punish them for it; and he was the rather led to make this public declaration, because he knew that the death of Abner in this way would be resented by the friends of Saul's family, and be an obstruction to the union of the two kingdoms, which it was known Abner was endeavouring to bring about. (i) Antiqu. l. 7. c. 1. sect. 6.