Scripture, 2 Samuel 24:1-25
Neither will I offer burnt offerings unto the Lord my God of that which doth cost me nothing. (2 Sam. 24:24)

You would think that when God had established David in his kingdom that he would have no more problems with people, conspiracy, or opposition. But this just wasn't so. Expect opposition when you are doing God's work. I used to tell our Youth for Christ workers to expect things to go wrong once in a while and then when they did, to look up and pray, "Lord, this is just what I was looking for. Help me now." And he will.

David made two great mistakes in his life. One was the matter of Uriah the Hittite; the other was numbering all the people of Israel and Judah, which obviously involved some self-will and a desire for personal glory. God was angry that David conducted such a census. But David was as great a repenter as he was a sinner and psalm writer. After David repented, he wanted to make an offering to the Lord. David went to Araunah the Jebusite and said, "I need your threshing floor as a place where I can offer a sacrifice." Araunah said, as you would have if the king had talked to you, "Go ahead, take it; it's yours. You're the king." But David replied, "No, I will surely buy it of thee at a price." So he bought the threshing floor and the oxen for fifty shekels of silver and offered burnt offerings and peace offerings to the Lord (24:25).

Small thought here
The value of your service for God very frequently is directly proportional to what it costs you. David said, "I'm not going to offer a sacrifice to God that didn't cost me anything." What is your service for God really costing? Is it a sacrifice or just a pleasant hobby?