The Lord not only stayed the plague, but through Gad He also instructed David to build an altar to the Lord on the threshing floor of Ornan, the Jebusite (1 Chron. 21:18).
The Lord was very specific about this and left no alternative in the matter.
Why this particular spot was chosen does not appear in the narrative, but later on in 2 Chronicles 3:1 we have this statement: "Then Solomon began to build the house of the LORD at Jerusalem in mount Moriah, where the Lord appeared unto David his father, in the place that David had prepared in the threshing floor of Ornan the Jebusite."
If David had been a grasping, selfish man, he might have looked on this as an opportunity to fulfill the will of God without any cost to himself.
He had been passed over when the plague struck men in Israel, and now a rich man had offered him a threshing floor for an altar and animals and grain for the offerings.
But David refused to bring before the Lord that which cost him nothing. "And the king said unto Araunah [Ornan], Nay; but I will surely buy it of thee at a price: neither will I offer burnt-offerings unto the LORD my God of that which doth cost me nothing" (2 Sam. 24:24).
What a tremendous lesson for us. It is one thing to serve on boards and committees that handle the affairs of others; it is quite another to make decisions that affect us personally.
It is not a sacrifice to the Lord if we give of that which costs us nothing.
"The sacrifices of God are a broken spirit: a broken and a contrite heart, O God, thou wilt not despise" (Ps. 51:17).