How do we know sanctification by the Spirit is true?

1 Peter 1:2 details that the elect are 'sanctified by the Spirit' which indicates the work of the Holy Spirit in the lives of believers. This sanctification is not merely about moral improvement but involves an essential separation from sin and being set apart for God's purposes. The Holy Spirit actively works in the believer's life, using the means of grace, especially the preaching of the gospel, to draw them unto holiness. Through Scripture, we understand that sanctification is an essential element of salvation and involves both being set apart and the continual process of becoming more like Christ, as expressed in 2 Thessalonians 2:13. Thus, this doctrine is vital for every believer as it reveals the Spirit's transformative power.