In addition to the initial work of conviction, repentance, and regeneration, the Spirit provides for the believer’s ongoing sanctification.
“God has chosen you from the beginning for salvation through sanctification by the Spirit and faith in the truth.” 2 Thessalonians 2:13
In that context “sanctification” means we have been set apart from sin and eternal death. That’s a positional sanctification resulting from our standing as believers in Christ. Our practical sanctification comes as the Spirit does His transforming work within us day by day.
“And we, who with unveiled faces all reflect the Lord’s glory, are being transformed into his likeness with ever-increasing glory, which comes from the Lord, who is the Spirit” – 2 Cor. 3:18
The Christian life begins in the power of the Spirit and includes all those aspects of His supernatural work within us. We cannot reach spiritual maturity by human means apart from His power.
“Sanctification” isn’t a popular word in our culture. “Sanctification” comes from two Latin words: sanctus which means holy, and ficare which means to make. So to sanctify means to make holy.
As rarely as the word sanctification may be in our culture, the reality is very crucial, very contemporary, and very relevant in the life of the believer.
John Piper gives some examples;
‘Suppose you’ve always concealed private sources of income when filling out your tax returns. Then you come to believe in Jesus Christ as Savior and Lord and begin to tell the truth on your tax returns—that’s sanctification. Suppose you’re always on your husband’s case, and then the Word of God pricks your conscience and you begin to preach less and look for ways to show respect—that’s sanctification. Suppose you’re sleeping with your girlfriend, and you meet Jesus Christ and get the courage to move out—that’s sanctification.’
“to remind you of them again, because of the grace God gave me 16 to be a minister of Christ Jesus to the Gentiles with the priestly duty of proclaiming the gospel of God, so that the Gentiles might become an offering acceptable to God, sanctified by the Holy Spirit” – Romans 15:15-16
The Santification through the Holy Spirit is seeing the grace of God conquer our rebellion and conform us to the likeness of Christ. The way to grow in sanctification is to fill yourself with the word of God (John 17:17) and the Spirit of God.
We open ourselves to the power of the Spirit in prayer and we seek to fill ourselves with his word in study. We pray, we pursue, we study, we work, for it is God who is at work in us to will and to do his good pleasure (Phil. 2:12-13)