1 Chronicles 11:4-6
4-6David and all Israel went to Jerusalem (it was the old Jebus, where the Jebusites lived). The citizens of Jebus told David, "No trespassing—you can't come here." David came on anyway and captured the fortress of Zion, the City of David. David had said, "The first person to kill a Jebusite will be commander-in-chief." Joab son of Zeruiah was the first; and he became the chief.
7-9David took up residence in the fortress city; that's how it got its name, "City of David." David fortified the city all the way around, both the outer bulwarks (the Millo) and the outside wall. Joab rebuilt the city gates. David's stride became longer, his embrace larger—yes, God-of-the-Angel-Armies was with him!