John 8:31-34 (NIV) - (31) To the Jews who had believed him, Jesus said, "If you hold to my teaching, you are really my disciples. (32) Then you will know the truth, and the truth will set you free." (33) They answered him, "We are Abraham's descendants and have never been slaves of anyone. How can you say that we shall be set free?" (34) Jesus replied, "I tell you the truth, everyone who sins is a slave to sin.
Romans 6:16 (NIV) - (16) Don't you know that when you offer yourselves to someone to obey him as slaves, you are slaves to the one whom you obey--whether you are slaves to sin, which leads to death, or to obedience, which leads to righteousness?