1 Chronicles 11:5-7

11:5 The residents of Jebus said to David, “You cannot invade this place!” But David captured the fortress of Zion (that is, the City of David). 11:6 David said, “Whoever attacks the Jebusites first will become commanding general!” So Joab son of Zeruiah attacked first and became commander. 11:7 David lived in the fortress; for this reason it is called the City of David.