Joab kills Amasa during the pursuit of Sheba, the Benjaminite who rebelled against David.
Sheba, wearing a turban, flees on horseback towards the right and looks back at the horsemen who pursue him at a distance. Riding at the head of the troop of armoured horsemen is Joab: he pulls the beard of Amasa, who was supposed to replace him as chief commander of David's armies, and pierces him with his sword.
20 Now a scoundrel named Sheba son of Bichri, a Benjaminite, happened to be there. He sounded the trumpet and cried out,“We have no portion in David,
no share in the son of Jesse!
Everyone to your tents, O Israel!”
2 So all the people of Israel withdrew from David and followed Sheba son of Bichri; but the people of Judah followed their king steadfastly from the Jordan to Jerusalem.
3 David came to his house at Jerusalem; and the king took the ten concubines whom he had left to look after the house, and put them in a house under guard, and provided for them, but did not go in to them. So they were shut up until the day of their death, living as if in widowhood.
4 Then the king said to Amasa, “Call the men of Judah together to me within three days, and be here yourself.” 5 So Amasa went to summon Judah; but he delayed beyond the set time that had been appointed him. 6 David said to Abishai, “Now Sheba son of Bichri will do us more harm than Absalom; take your lord’s servants and pursue him, or he will find fortified cities for himself, and escape from us.” 7 Joab’s men went out after him, along with the Cherethites, the Pelethites, and all the warriors; they went out from Jerusalem to pursue Sheba son of Bichri. 8 When they were at the large stone that is in Gibeon, Amasa came to meet them. Now Joab was wearing a soldier’s garment and over it was a belt with a sword in its sheath fastened at his waist; as he went forward it fell out. 9 Joab said to Amasa, “Is it well with you, my brother?” And Joab took Amasa by the beard with his right hand to kiss him. 10 But Amasa did not notice the sword in Joab’s hand; Joab struck him in the belly so that his entrails poured out on the ground, and he died. He did not strike a second blow.
Then Joab and his brother Abishai pursued Sheba son of Bichri.
(2 Samuel 20:1-10)