Therefore, I urge you, brothers, in view of God's mercy, to offer your bodies as a living sacrifice, holy and pleasing to God -- this is your spiritual act of worship.
In view of God's mercy - The Bible says that ALL have sinned and deserve death. (Rom. 3:23; 6:23). But God sent His only Son to pay that price. Because of His mercy, we have forgiveness of our sins and we can enter in to a right relationship with Him.
Offer your bodies as a living sacrifice - In the Old Testament, according to God's law, a priest would kill an animal, cut it in pieces, and place it on the altar as a sacrifice. Sacrifice was very important. But the Word also says, "To obey is better than sacrifice." (1 Sam. 15:22) To offer our bodies as a sacrifice, we must lay aside our own desires and follow God.
Holy and pleasing to God - Our lives are to be set apart. We shouldn't conform to the world, because we don't belong to the world. We belong to God; we are to be holy, for He is holy. (1 Pet. 1:16) This way of living is pleasing to God.
This is your spiritual act of worship - As we grow closer to God, we develop the mind of Christ. We begin to look like Jesus, think like Jesus, and act like Jesus. We willingly lay down our will for His. This is our act of worship that is pleasing to God.