Joab had treacherously murdered Abner and Amasa under David’s kingship. What Joab had done was an outstanding debt. Solomon transfers this guilt from his father David and from himself to Joab and Joab’s descendants. He means: “If Joab’s death does not entirely take away the guilt, I will put it on his children.” God does not tolerate guilt; it needs to be removed.
31 The king replied to him, “Do as he has said, strike him down and bury him, and thus take away from me and from my father’s house the guilt for the blood that Joab shed without cause.