John 8:32

And you will know the truth (regarding salvation), and the truth will set you free (penalty of sin). So if the Son makes you free, then you are unquestionably free.  

We who are born again have been set free from sin by Jesus. All the old self and sins have washed away. If the devil tries to bring up the old memories of sin, we reject and cast down that memory. We remind the devil of John 8:32 by quoting the scripture and keep reminding him each time he brings the memory up. The devil will flee before the Word of God.