Joab: Son of David's Sister: Kills Amasa

And while they were at the great stone in Gibeon, Amasa joined them. Now Joab was dressed in military attire, with a dagger strapped to his belt. And as he stepped forward, he slipped the dagger from its sheath. …

Moreover, you know what Joab son of Zeruiah did to me—what he did to Abner son of Ner and Amasa son of Jether, the two commanders of the armies of Israel. He killed them in peacetime to avenge the blood of war. He stained with the blood of war the belt around his waist and the sandals on his feet.