1 Chronicles 20:1-2

20:1 In the spring, at the time when kings normally conduct wars, Joab led the army into battle and devastated the land of the Ammonites. He went and besieged Rabbah, while David stayed in Jerusalem. Joab defeated Rabbah and tore it down. 20:2 David took the crown from the head of their king and wore it (its weight was a talent of gold and it was set with precious stones). He took a large amount of plunder from the city.