There is this idea in Christianity that mankind has been created in the image and likeness of God, possessing both reason and morality. Though man fell from that prestigious place of grace, he has nonetheless retained the imago dei (the image of God), albeit in a corrupt state of being. The early church father Origen stated that the image of God still existed within fallen man, but that it was like a treasure buried deep within a well, covered by dirt and debris. Think of it as though the imago dei were once a mosaic that once depicted the most beautiful scene imaginable, but now the mosaic has been covered by dirt and filth. You see bits and pieces of the beautiful image, but you cannot quite make out what it is exactly due to all the grime caked on it. This is how it is with humanity. There are still bits and pieces of the divine image that are seen in man, such as when we love one another and do good things for the betterment of humanity. Still, there is a lot more dirt and filth that can be seen in our race (as the news reports will clearly show).
Christian theology has always maintained that in salvation God seeks to remedy this situation via a process known as sanctification. Sanctification is a distinct work from justification (where a person is declared righteous before God by his faith in Christ), and naturally flows from justification provided the person in question does not resist the process. Sanctification is a process in which the Holy Spirit works upon the heart and soul of the believer and gradually changes him or her into the image of Christ. It is the process whereby we participate in the holiness of God.
Sanctification has been a common motif since the beginning of the Church, and one can clearly find it in all of the New Testament authors, as well as in the early church fathers. St. Paul, writing to the Thessalonians, has this to say concerning the will of God for his children:
For you know what instructions we gave you through the Lord Jesus. For this is the will of God, your sanctification: that you abstain from fornication; that each one of you knows how to control your own body in holiness and honour, – I Thessalonians 4:2-4.
Lest anyone should think that growing closer to God and becoming more like him is only for certain people, the Apostle clearly tells us that it is the will of God that every believer should be sanctified and that they should learn to control their bodies in holiness and honor. This applies to everyone who professes to be a follower of Christ. God desires your sanctification, and he longs for you to be like him. St. Peter says this concerning the sanctification of the believer:
His divine power has given us everything needed for life and godliness, through the knowledge of him who called us by his own glory and goodness. Thus he has given us, through these things, his precious and very great promises, so that through them you may escape from the corruption that is in the world because of lust, and may become participants in the divine nature. – II Peter 1:3-4.
What does it mean to be made “partakers of the divine nature” exactly? The eastern church approaches this question by saying that we go through the process of theosis or deification, whereby we become more and more like God in terms of his moral attributes and character. This is also supported by the early father St. Athanasius, who wrote that “God became man so that man might become god.” Athanasius certainly was not suggesting that we can become divine by nature, but that we can become more like God in terms of his holiness and character. We take on the attributes of God in our manners and actions. Another father, St. Cyril of Alexandria wrote this concerning the process:
… when Christ has come to be within us He lulls to sleep the law that rages in the members of flesh. He rekindles our reverence towards God, while simultaneously causing the passions to atrophy. He does not reckon our faults against us. Instead, He tends us as a doctor would his patients. For He binds up that which has been wounded, He raises that which has fallen, as a good shepherd who has laid down His life for His sheep. – (Cyril of Alexandria: The Early Church Fathers; Routledge pg. 119)
Basically, what God does in the process of sanctification is that he becomes like a person intent on restoring that beautiful mosaic to its former beauty. God begins to wash that mosaic, cleaning off the dirt and grime and filth, until we can finally start to see the beautiful image that lies underneath. He even retouches the faded colors and adds touches that were not there to begin with! He does this because he desires to see that beautiful image restored to its former glory. There are Christians who, unfortunately, believe that during this life we shall always remain sinful, broken people that God sort of has to drag along until we reach the other side. This is sad because it really denies the best part of the good news (which is more than not going to hell) which is to be restored to the way that God meant us to be. In sanctification God rights the wrong done to us by Satan, and sets us up as moral examples whereby we are able to lead others to him. Prior to giving my life to the Lord, I did not think much of people who claimed to be Christians but who acted exactly the same as those who did not know God, but I highly respected those who I knew were different. That is what the lost need to see in Christians, something different that makes them curious, hungry even for whatever it is we have that makes us different! They should look at us, see how happy we are, how good we are to others, that it sparks a flame within their bosom that causes them to want the same thing.
Does being sanctified mean that the Christian never sins or that he is completely perfect in every way? By no means! What it does mean, however, is that the Christian fulfills what Christ said when he spoke of the two greatest commandments: Love the Lord your God with all your heart, your mind, your soul and your strength, and love your neighbor even as yourself. This is what sanctification does to the human heart; this is what Christian Perfection truly is!
I’ll conclude by quoting C.S. Lewis on this topic.
The command Be ye perfect is not idealistic gas. Nor is it a command to do the impossible. He is going to make us into creatures that can obey that command. He said (in the Bible) that we were ‘gods’ and He is going to make good His words. If we let Him—for we can prevent Him, if we choose—He will make the feeblest and filthiest of us into a god or goddess, a dazzling, radiant, immortal creature, pulsating all through with such energy and joy and wisdom and love as we cannot now imagine, a bright stainless mirror which reflects back to God perfectly (though, of course, on a smaller scale) His own boundless power and delight and goodness. The process will be long and in parts very painful, but that is what we are in for. Nothing less. He meant what He said. – C.S. Lewis, Mere Christianity 205-206.