What is sanctification? I find greatest clarity in John 8 and 1 John about those who believe still needing to be free from slavery to sin. If you sin, says Jesus, you are a slave to sin, and He said it even to those who believed. To me this explains that justification by faith still needs to be followed by sanctification. In John 8 it is first believers following Jesus by adhering to His teachings then Jesus Himself sanctifying them setting them free from sin (which I personally equate to sanctification) through these followers knowing the truth. Truth, Jesus stated later in His prayer for the disciples before His crucifixion, sanctifies. "Sanctify them by your truth", He prayed to the Father, "Your word is truth." Now my own feeling is that the logic is given by Jesus that if by sinning it is slavery to sin then any sin is slavery so to be free from thiscslavery means no longer sinning. It is not hard and fast it seems when you consider that life has to be given by God to a person once set free but sinning afterwards as John teaches in his epistle 1 John. So it isn't an exact science. Another factor is rebirth of the Spirit that comes with this sanctification. The one sinning is of Satan - believing but not yet sanctified. Spirit transforms into one not sinning and this makes them a child of God in the sense Jesus meant it. This is by hearing Jesus' words of spirit (or the gifts or anointing it later is added in John' epistle). It involves love toward Jesus so the words are nor rejected. For a parallel in Pauline teaching (teachings of Apostle Paul) there is his message to Ephesians that they were taught in accordance with the truth that is Jesus to put off falsehood and speak truth ... to be angry and not sin ... to not give a foothold to Satan - paralelling John 8 and 1 John which is interesting because the Ephesians may historically have received this directly from John in Ephesus.
