Charles Spurgeon Commentary 1 Chronicles 21:18-27

"Then the angel of Jehovah commanded Gad to say to David, that David should go up, and rear an altar unto Jehovah in the threshing-floor of Ornan the Jebusite. And David went up at the saying of Gad, which he spake in the name of Jehovah. And Ornan turned back, and saw the angel; and his four sons that were with him hid themselves. Now Ornan was threshing wheat. And as David came to Ornan, Ornan looked and saw David, and went out of the threshing-floor, and bowed himself to David with his face to the ground. Then David said to Ornan, Give me the place of this threshing-floor, that I may build thereon an altar unto Jehovah: for the full price shalt thou give it me, that the plague may be stayed from the people. And Ornan said unto David, Take it to thee, and let my lord the king do that which is good in his eyes: lo, I give [thee] the oxen for burnt-offerings, and the threshing instruments for wood, and the wheat for the meal-offering; I give it all. And king David said to Ornan, Nay; but I will verily buy it for the full price: for I will not take that which is thine for Jehovah, nor offer a burnt-offering without cost. So David gave to Ornan for the place six hundred shekels of gold by weight. And David built there an altar unto Jehovah, and offered burnt-offerings and peace-offerings, and called upon Jehovah; and he answered him from heaven by fire upon the altar of burnt-offering. And Jehovah commanded the angel; and he put up his sword again into the sheath thereof." — 1 Chronicles 21:18-27 (ASV)

Then the angel of the LORD commanded Gad to say to David, that David should go up, and set up an altar to the LORD in the threshing floor of Ornan the Jebusite. And David went up at the saying of Gad, which he spoke in the name of the LORD. And Ornan turned back, and saw the angel; and his four sons with him hid themselves. Now Ornan was threshing wheat. And as David came to Ornan, Ornan looked and saw David, and went out of the threshing floor, and bowed himself to David with his face to the ground. Then David said to Ornan, Grant me the place of this threshing floor, that I may build an altar there to the LORD: you shall grant it me for the full price: that the plague may be stayed from the people. And Ornan said to David, Take it to you, and let my lord the king do that which is good in his eyes: look, I give you the oxen also for burnt offerings, and the threshing instruments for wood, and the wheat for the meat offering; I give it all. And king David said to Ornan, No; but I will truly buy it for the full price: for I will not take that which is yours for the LORD, nor offer burnt offerings without cost. So David gave to Ornan for the place six hundred shekels of gold by weight. And David built there an altar to the LORD, and offered burnt offerings and peace offerings, and called upon the LORD, and he answered him from heaven by fire upon the altar of burnt offering. And the LORD commanded the angel; and he put up his sword again into the sheath of it.

See what was done by David's intercession and sacrifice; and remember that there is a greater David who, with a richer sacrifice and mightier intercession, sheathes the sword of God, so that his people are spared.