1 Chronicles 20:1-2

1Then it happened at the end of the year, at the time when kings go out to battle, Joab led out the army and ravaged and devastated the land of the Ammonites, and came and besieged Rabbah. But David stayed at Jerusalem [with Bathsheba]. Joab struck Rabbah and overthrew it.

2David took the crown of their king from his head and found that it weighed a talent of gold and that there was a precious stone in it; so it was set on David’s head. He also brought a very great amount of spoil (plunder) out of the city [of Rabbah].