20 For when you were servants of sin, you were free from righteousness.
Romans 6:20 Cross References - Living_Oracles
John 8:34
34 Jesus replied, Most assuredly, I say to you, whosoever commits sin is a slave of sin.
Romans 6:16-17
16 Do you not know, that to whom you present yourselves servants, by obedience; his servants you are whom you thus obey; whether of sin into death, or of obedience into righteousness?
17 But, thanks to God, that though you were the servants of sin; yet you have heartily obeyed that model of doctrine to which you have been given up.