Sanctify them through thy truth: thy word is truth." (John 17:17).
When a baby is born, everyone can see, or thinks he can see the family likeness. That likeness becomes more obvious as the child grows. This is true of the Christian also. "If ye know that he is righteous, ye know that everyone that doeth righteousness is born of him" (1 John 2:29).
The Big Break
When a sinner trusts Christ as his Saviour, he is immediately freed from the guilt of sin. He is justified, or declared righteous by God. But because this faith is the result of God changing his heart (called being ‘born again’) it always marks the beginning of a changed life. He begins to love and serve his Lord and Saviour Jesus Christ in thankfulness to him.
The word "sanctified" means to be made holy or separate from sin and devote to the service of the Lord. When someone becomes a Christian, as well as being forgiven, his life takes on a new direction as he begins to give up his sinful ways. In this sense, the Bible calls every Christian sanctified" or a saint (i.e. one who is holy or separated 1 Peter 1:2, 1 Corinthians 6:11, Ephesians 1:1 etc).
The Longer Run
Although every Christian is a changed person, he is not perfectly changed. Far from it. Between becoming a Christian and going to Heaven the Christian life is one of imperfect holiness. All his life, the Christian is to seek to "grow in grace and in the knowledge of our Lord and Saviour" (2 Peter 3:18). One feature of this growth is an increasing awareness of sins he hadn’t even noticed before. The conflict between his God-given new nature and the remains of sin is a constant element of the Christian life (Galatians 5:17).
Despite his ups and downs, his failures and falls, the overall pattern of his life will be one of becoming more and more like Christ as the Spirit of God works in him day to day through the Word of God. "Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ" (Philippians 1:6).
The Finishing Post
When the Christian goes to Heaven, he will the be perfectly free from the power and presence of sin in him. He will be like Christ. "We shall be like him, for we shall see him as he is (1 John 3:2).
The Bible does not lay the emphasis on how well a man can say he has become a Christian, but on the evidence of the fact in a changed life. A Christian has changed, is being changed and will be changed. Are you a real Christian or have you just learnt a few well-known words and phrases that Christians use? Christ’s death on the cross as an atonement for sin gives every believer a title to Heaven. But those who have such a title are also being prepared for its enjoyment. Are you being changed "from glory to glory, even as by the Spirit of the Lord" (2 Corinthians 3:18)?