Romans 6 begins with the reminder that when we come to Christ we receive new life.  That born-again life is not to be given back to sin and unrighteousness, but it is to be given to God by a life of right living (righteousness).  The result of presenting ourselves to God is sanctification.  We were dead in trespasses and sins (Ephesians 2) and Christ brought us back to life.  That new life has to be lived for the One who gave it to you. We who were once slaves to the bad master Sin have been set free to be slaves to a good God.  The only freedom there is, is to be made free from sin so that we can be free to serve God.

“Present yourselves to God as those alive from the dead, and your members as instruments of righteousness to God….For just as you presented your members as slaves to impurity and to lawlessness, resulting in further lawlessness, so now present your members as slaves to righteousness, resulting in sanctification…and the outcome, eternal life.” Romans 6:13,19, 22 (NASB)