I do not ask that you take them out of the world, but that you keep them from the evil.  They are not of the world, just as I am not of the world. Sanctify them in the truth; your word is truth. As you sent me into the world, so I have sent them into the world.  And for their sake I consecrate myself, that they also may be sanctified in truth.  (John 17:15-19)

In his final, extended prayer for his disciples, Jesus asks his Heavenly Father to sanctify them.  The complexity of this prayer is revealed by understanding that ‘sanctify’ translates the Greek verb ἁγιάζω (hagiazó), which means ‘to make holy’ but also has the plainer meaning ‘to set apart’.

If we substitute, ‘sanctify’ with ‘set apart’ the prayer reads thus:

 I do not ask that you take them out of the world, but that you keep them from the evil.  They are not of the world, just as I am not of the world.  Set them apart in the truth; your word is truth. As you sent me into the world, so I have sent them into the world.  And for their sake I consecrate myself, that they also may be set apart in truth.

Jesus was incarnate and holy, that is, he was inherently righteous and untainted by the world, yet his imminent witness and presence is essential to the redemptive purpose of God the Father.  It is Jesus’ prayer that his disciples are not ‘spirited away’ but remain in the world.  It is their witness and presence that will represent Jesus after his death, resurrection and ascension.

In Romans, Paul reveals how Jesus’ prayer is outworked.  Righteousness is granted through faith.  There is no verbal form of ‘righteousness’ in English (the nearest would be to say ‘to make righteous’) so the verb is ‘to justify’. 

… for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus,whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.  (Romans 3:23-26)

In this way then, the faithful disciple is set apart from the evil of the world and is made holy.  Justification is a process of location, if you will – and it is all God’s work, because even faith itself is gifted, as Paul writes in another epistle, this time to church in Ephesus:

For by grace, you have been saved through faith. And this is not your own doing; it is the gift of God,not a result of works, so that no one may boast.  (Ephesians 2:8-9)

Jesus’ righteousness is then imputed through faith and that faith is bestowed, so this changes the spiritual location of the disciple if not the physical one.  This accords with Jesus’ prayer for the disciples not to be removed from earth but to remain earth-bound.

However, there is one big difference between Jesus and all his disciples.  Jesus was morally holy.  His every thought, word and deed was righteous – as the writer of Hebrews says of him:

 For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens. (Hebrews 7:26)

And Paul says,

 For our sake, (God the Father) made (his Son, Jesus) to be sin who knew no sin, so that in him we might become the righteousness of God.  (2 Corinthians 5:21)

Justification may re-position the disciple in respect of God, but it does not mean that like Jesus that the disciple will now be free of sinful ways.  Taken another way then, sanctification becomes a destination to be reached in death, or a goal of completion, to be realised when the disciple stands resurrected in the presence of Jesus, as Paul prays for his brothers and sisters in Christ in Thessalonica:

Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ.  (1 Thessalonians 5:23)

Also,

When Christ who is your life appears, then you also will appear with him in glory. (Colossians 3:4)

This then is glorification, the completion of sanctification.  Once more, this is all God’s sovereign work, by which humanity might benefit, be restored and reconciled to the creator.  Paul describes the full redemptive undertaking:

And we know that for those who love God all things work together for good, for those who are called according to his purpose. For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers.  And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified. (Romans 8:28-30)

Foreknown, predestined, called, justified and glorified but no mention of sanctified in this list, (unless we count justification and glorification as ‘positional’ and ‘ultimate’ sanctification, respectively) and that is because there is another meaning to sanctification, which is that of a process – a process, moreover, that is not entirely God’s work but requires the full engagement and self -dedication of the disciple – and this is to address the plain fact, that when a sinful person is justified, they still inhabit the sinful world and their own sinfully inclined ‘flesh’.

Paul describes this beautifully:

For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree with the law, that it is good.  So now it is no longer I who do it, but sin that dwells within me.  For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing.  Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.  (Romans 7:15-20)

And by ‘flesh’ (a direct translation of σάρξ sarx) it is important to understand this a term which embraces all aspects of corporality, not only the body and senses but the mind with its rapacious desire.  Indeed, the exact same holistic sense that is conveyed in the greatest command, where all are commanded to love the God ‘with all your heart and with all your soul and with all your mind’ (Matthew 22:37).

Paul exposes the tension in the spiritually awakened, indeed enlivened and reborn disciple, and the pull of the world and his desire for it.

Sanctification is then a battle where the battlelines are drawn across the very heart, mind and soul of the disciple.  The manifestation of this warfare is separation from the world, and the means? Jesus makes it clear what is required, nothing less than complete self-denial.  He tells his disciples

‘If anyone would come after me, let him deny himself and take up his cross and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake will find it. For what will it profit a man if he gains the whole world and forfeits his soul?’  (Matthew 16:24-26)

Sanctification then is also the conscious, deliberate and diligent act of re-dedication.  Paul writes this:

I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. (Romans 12:1)

Note that Paul makes the statement a plea, and this is because he knows that this process is a continual act of the will; difficult to sustain, yet nonetheless critical.  In the process of sanctification, holiness is then is both bestowed and attained.  Peter similarly exhorts the authentic follower of Jesus to be… 

… as obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct, since it is written, ‘you shall be holy, for I am holy.’  (1 Peter 1:14-16)

And this is all the harder because the reminder of what delighted and stimulated remains, and requiring rejection, another apostle, John, makes a pleads:

Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world – the desires of the flesh and the desires of the eyes and pride in possessions – is not from the Father, but is from the world. And the world is passing away along with its desires, but whoever does the will of God abides for ever.  (1 John 2:15-17)

In fact, John reports what Jesus says more starkly:

Whoever loves his life loses it, and whoever hates his life in this world will keep it for eternal life.  (John 12:25)

So, a failure to engage in the sanctification has eternal consequences.  And remember, Jesus does not expect his followers to set themselves apart from the world even if his Father, in justifying any, has ‘set them apart’, Paul makes this clear:

I wrote to you in my letter not to associate with sexually immoral people – not at all meaning the sexually immoral of this world, or the greedy and swindlers, or idolaters, since then you would need to go out of the world.  (Romans 5:9-10)

The disciple has both help and a helper, the Holy Spirit, (John 14:15-17 & 26); but the daily task of seeking holiness is the struggle to overcome and it must be so to create the witness to the truth to the world:

 Strive for… the holiness without which no one will see the Lord. (Hebrews 12:14)