Then the angel of the LORD commanded Gad to say to David, that David should go up, and set up an altar unto the LORD in the threshingfloor of Ornan the Jebusite.
The angel of the Lord commanded Gad to say ... The order about the erection of an altar, as well as the indication of its site, is described, 2 Samuel 24:18, as brought directly by Gad. Here we are informed of the quarter whence the prophet got his commission. It is only in the later stages of Israel's history that we find angels employed in communicating the divine will to the prophets.
The threshing-floor of Ornan the Jobusite. It appears that long after David had taken the fortress of Jebus and fixed his residence there, Jerusalem was not the exclusive property of any one tribe. Judah and Benjamin continued without doubt to inhabit it, in brotherly communion, and the Jebusite lived there, as before, along with his new masters.