1Kgs 2:5

“[David] orders Solomon to punish [Joab], not out of viciousness or hatred for him but because he knew that he was wicked and that, if he had acted with hostility against him who was a mature man, he would act even worse against a young man, so that the kingdom would become unstable, and the house would not be firmly established. Therefore he entrusts his son with the revenge against him who had offended him, in order that, after the killing of that evil man by the hand of the new king, he might be feared by everyone, and no revolt might ever occur.”

“thou knowest also what Joab . . . did--The insolent and imperious conduct of that general had not only been deeply offensive to the feelings (Sa2 18:5-15; Sa2 19:5-7), but calculated to bring reproach on the character, to injure the prospects, and endanger the throne of David. Passing over the injuries committed directly against himself, David dwelt with strong feelings on the base assassination of Abner and Amasa. shed the blood of war in peace, &c.--The obvious meaning is, that in peace he acted towards them as if they had been in a state of warfare; but perhaps these graphic expressions might be designed to impress Solomon's mind more strongly with a sense of the malice, treachery, and cruelty by which those murders were characterized.”