2 Samuel 3:28
And afterward when David heard it, he said, I and my kingdom are guiltless before the LORD for ever from the blood of Abner the son of Ner: And afterward when David heard it, he said, I and my kingdom are guiltless before the LORD for ever from the blood of Abner the son of Ner:
Abner had broken with Ishbosheth and set out to bring all Israel over to David when Joab treacherously murdered him, and the verse is David's answer to that murder. In it David declares himself and his kingdom guiltless before the Lord forever from Abner's blood, laying the guilt upon Joab and his father's house. He does not visit the crime with just retribution because the kingdom is still unsettled and Joab and his brother Abishai are too powerful in position, so he leaves them to the justice of God. He publicly shows his abhorrence of the deed by giving Abner burial with public honors, requiring the army with Joab at its head to mourn in rent garments and sackcloth, fasting himself on the burial day, and following the bier as chief mourner. At the grave he speaks an elegy over Abner that rebukes the murderers.