1 Chronicles 20:1-3

That spring, the time when kings usually go off to war, Joab led the army out and ravaged the Ammonites. He then set siege to Rabbah. David meanwhile was back in Jerusalem. Joab hit Rabbah hard and left it in ruins. David took the crown off the head of their king. Its weight was found to be a talent of gold and set with a precious stone. It was placed on David’s head. He hauled great quantities of loot from the city and put the people to hard labor with saws and picks and axes. This is what he did to all the Ammonites. Then David and his army returned to Jerusalem.