Then the angel of the LORD ordered Gad to tell David to go up and build an altar to the LORD on the threshing floor1 of Araunah the Jebusite.
References for 1 Chronicles 21:18
So David went up in obedience to the word that Gad had spoken in the name of the LORD.
While Araunah was threshing wheat,2 he turned and saw the angel; his four sons who were with him hid themselves.
References for 1 Chronicles 21:20
Then David approached, and when Araunah looked and saw him, he left the threshing floor and bowed down before David with his face to the ground.
David said to him, "Let me have the site of your threshing floor so I can build an altar to the LORD, that the plague on the people may be stopped. Sell it to me at the full price."
Araunah said to David, "Take it! Let my lord the king do whatever pleases him. Look, I will give the oxen for the burnt offerings, the threshing sledges for the wood, and the wheat for the grain offering. I will give all this."
But King David replied to Araunah, "No, I insist on paying the full price. I will not take for the LORD what is yours, or sacrifice a burnt offering that costs me nothing."
So David paid Araunah six hundred shekels of gold for the site.
References for 1 Chronicles 21:25
David built an altar to the LORD there and sacrificed burnt offerings and fellowship offerings. He called on the LORD, and the LORD answered him with fire3 from heaven on the altar of burnt offering.
References for 1 Chronicles 21:26
Then the LORD spoke to the angel, and he put his sword back into its sheath.