Romans 12:1 I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service.

We are called to be a living sacrifice for God.  In the old testament, they would sacrafice animals for sin. When someone made a sacrafice to God it was to honor God in thanksgiving or asking for forgiveness for their sins. 

In fact, Hebrews 9:22 says: In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness

In the new testament, we know that Jesus Christ was our sacrafice on the cross. Jesus paid our sin debt. Praise the Lord!

We are called to be a people that honors God and we do that through living a life that is pleasing to Him. A holy life is one that is set apart and dedicated to God. This is our resonable service. In other words, this is the fair and sensible thing to do.