1 Kings 2:5-6, 31-33

Moreover thou knowest also what Joab the son of Zeruiah did unto me, even what he did to the two captains of the hosts of Israel, unto Abner the son of Ner, and unto Amasa the son of Jether, whom he slew, and shed the blood of war in peace, and put the blood of war upon his girdle that was about his loins, and in his shoes that were on his feet. Do therefore according to thy wisdom, and let not his hoar head go down to Sheol in peace.

And the king said unto him, Do as he hath said, and fall upon him, and bury him; that thou mayest take away the blood, which Joab shed without cause, from me and from my father’s house. And Jehovah will return his blood upon his own head, because he fell upon two men more righteous and better than he, and slew them with the sword, and my father David knew it not, to wit, Abner the son of Ner, captain of the host of Israel, and Amasa the son of Jether, captain of the host of Judah. So shall their blood return upon the head of Joab, and upon the head of his seed for ever: but unto David, and unto his seed, and unto his house, and unto his throne, shall there be peace for ever from Jehovah.