20 When you were slaves of sin, you were free in regard to righteousness.
Romans 6:20 Cross References - Common
John 8:34
34 Jesus answered them, "Truly, truly, I say to you, everyone who commits sin is a slave of sin.
Romans 6:16-17
16 Do you not know that if you yield yourselves to any one to obey as slaves, you are slaves of the one whom you obey, whether of sin, which leads to death, or of obedience, which leads to righteousness?
17 But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed,