Thematic Bible: David was false to joab

"You also know what Joab son of Zeruiah did to me and what he did to the two commanders of Israel's army, Abner son of Ner and Amasa son of Jether. He murdered them [in a time] of peace to avenge blood shed in war. He spilled that blood on his own waistband and on the sandals of his feet. Act according to your wisdom, and do not let his gray head descend to Sheol in peace.