2 Samuel 20:6-8

6Then David said to Abishai, ‘Bicri's son, Sheba, will cause us more trouble than Absalom did. Take my soldiers and chase after him. If you do not catch him, his people will hide in towns with strong walls. Then he will escape from us.’

7So Abishai took Joab's soldiers, as well as the king's personal guards, the Pelethites and the Kerethites. He and all the king's soldiers marched out from Jerusalem to find Sheba.

8When they arrived at the big rock in Gibeon, Amasa came to meet them. Joab was wearing his soldier's clothes. He had a long knife that was tied to his belt. As Joab went towards Amasa, the knife fell to the ground.