2 Samuel 24:20-24

24:20 When Araunah looked out and saw the king and his servants approaching him, he went out and bowed to the king with his face to the ground. 24:21 Araunah said, “Why has my lord the king come to his servant?” David replied, “To buy from you the threshing floor so I can build an altar for the Lord, so that the plague may be removed from the people.” 24:22 Araunah told David, “My lord the king may take whatever he wishes and offer it. Look! Here are oxen for burnt offerings, and threshing sledges and harnesses for wood. 24:23 I, the servant of my lord the king, give it all to the king!” Araunah also told the king, “May the Lord your God show you favor!” 24:24 But the king said to Araunah, “No, I insist on buying it from you! I will not offer to the Lord my God burnt sacrifices that cost me nothing.”

So David bought the threshing floor and the oxen for fifty pieces of silver.