17 And Jesus answering said unto them, Render to Caesar the things that are Caesar’s, and to God the things that are God’s. And they marvelled at him.
1 Corinthians 6:19-20
19 What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
20 For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God’s.
-The Lord is nothing if not fair. In Mark 12, we see Him asking for things that belong to Him anyway; that seems reasonable enough to me. What are the most important things that we should be rendering unto God? According to 1 Corinthians 6, it is our body and our spirit. To those who have been redeemed, we are purchased from damnation and brought into the ownership of the Lord. Even if you have not accepted this truth, you still belong to God since He created all of us anyway. We should think, do, and say things that are profitable to God (Colossians 3:17), and we should live our lives not concerned with how things impact us, but how they impact the Lord.