I enjoyed preaching on Romans 12:1-8 yesterday. You can hear what I said here if you want to. I have been carrying on thinking about two specific things.
On one level it is true to say that the Gospel changes everything. But for a good Jew at the time of Jesus there would be a need to work out what precisely needs to change concerning sacrifice and idolatry. Everything, something or nothing?
Romans 12:1-2 is where sacrifice and idolatry meet.
Genesis 1 describes people as being made in the image of God. The Law later explains how inappropriate images, especially graven ones, are. You shall not bow down to them or worship them. Why not? Because human beings are the pinnacle of God's creation. If you want to know what God is like you should see more clues looking at a person than an idol. We are the idol. And the understanding of an idol is that it is the object of worship.
The Law also describes, in minute detail, the appropriate sacrifice for particular sins or occasions of uncleanness. The sacrificial animal industry was quite developed by Jesus' day and it was probably such marketeers that Jesus drove from the Temple Courts.
So Romans 12 introduces the idea that our very image, our body, should not like an idol be what is worshipped but what does the worshipping. This idol offers to God; it does not receive as if it were a god. How? Not by sacrificing but by being alive.
And that will involve a massive change of mind-set. The one who felt unworthy and needed to strangle a pigeon to be acceptable is now able to worship by serving, by going about, by simply being human. If you need a massive change of mind-set you need to allow God to work that in you. Let him transform you by the renewing of your mind. Not do-it-yourself but let-it-happen.
Then, amazingly, the second half of v2 suggests you will get to the point where you know, you actually know, what God's will is. After testing and approval sadly so there is no short-cut.
But those two verses were bad news for shepherds. Remember, the demand for sacrificial lamb can go down as well as up.