1 Chronicles 21:16-20

Then David raised his eyes and saw the angel of the Lord standing between earth and heaven, with his drawn sword in his hand stretched out over Jerusalem. Then David and the elders, covered with sackcloth, fell on their faces.

And David said to God, “Is it not I who commanded to count the people? Indeed, I am the one who has sinned and acted very wickedly, but these sheep, what have they done? Lord, my God, just let Your hand be against me and my father’s household, and not against Your people as a plague.” David’s Altar

Then the angel of the Lord commanded Gad to say to David, that David was to go up and build an altar to the Lord on the threshing floor of Ornan the Jebusite.

So David went up at the word of Gad, which he spoke in the name of the Lord.

Now Ornan turned back and saw the angel, and his four sons who were with him hid themselves. And Ornan was threshing wheat.