Then the king said to Amasa, “Call the men of Judah together to me within three days, and be here yourself.” So Amasa went to summon Judah, but he delayed beyond the set time that had been appointed him. And David said to Abishai, “Now Sheba the son of Bichri will do us more harm than Absalom. Take your lord’s servants and pursue him, lest he get himself to fortified cities and escape from us.” And there went out after him Joab’s men and the Cherethites and the Pelethites, and all the mighty men. They went out from Jerusalem to pursue Sheba the son of Bichri. When they were at the great 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 on his thigh, and as he went forward it fell out. And 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. But Amasa did not observe the sword that was in Joab’s hand. So Joab struck him with it in the stomach and spilled his entrails to the ground without striking a second blow, and he died. Then Joab and Abishai his brother pursued Sheba the son of Bichri. 2 Samuel 20:4-10.
Now that Absalom is out of the picture, David is more his old self, crushing his enemies and staying in charge. Sheba may have misread David’s flight from Jerusalem as a general weakness that could be exploited. But David is cleaning house now, even putting away his concubines who Absalom had publicly seduced or raped during the takeover.
Joab is still Joab, and when he sees his replacement, Amasa, has disobeyed David, he smells a rebel and takes him out. He will also ruthlessly pursue Sheba and come home with his head. The fortified city where Sheba is hiding recognizes Joab and gives up their fugitive on demand rather than be under siege by him.
The application for us is not a command to do violence, but to ruthlessly pursue unity. The church today is fragmented and split into many different agendas, led by people who are unwilling to work together. A kingdom divided will not stand.